FURUNO GNSS Receiver
Model
GT-88
eSIP Protocol Specifications
(Document No. SE18-600-003-00)
www.furuno.com
GT-88
Protocol Specifications
SE18-600-003-00
IMPORTANT NOTICE
No part of this manual may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying and recording, for any purpose without the express written permission of
the publisher, FURUNO ELECTRIC CO., LTD.
FURUNO ELECTRIC CO., LTD. All rights reserved.
All brand and product names are registered trademarks, trademarks or service marks of their respective
holders.
The following satellite systems are operated and controlled by the authorities of each government.
GPS, SBAS (WAAS): USA
GLONASS: Russia
Galileo, SBAS (EGNOS): Europe
QZSS, SBAS (MSAS): Japan
SBAS (GAGAN): India
FURUNO is not liable for any degradation while using these satellite systems. FURUNO cannot guarantee
specifications if any of these systems experience degradation. Based on these conditions the user is expected
to be familiar with these systems and is fully responsible for their use.
This document describes the eSIP protocol specifications for the following products.
・GT-88
・ePV7010B (eRideOPUS 7 chip 64 pin with GT-88 software)
Although this product is paying attention to compatibility with the past products, due to the correspondence to
various additions of specifications, some actions may differ unavoidably. Regarding the specifications, the
contents described in this document are set as ture, and for items not described in this document, the actual
operations of this product are set as true. For this product, if you need items compatible with past products,
please consult us before mass-producing this product.
We pay through attention about the software of this product. But, if perchance you found a bug or a trouble,
please feel free to contact us directly. We will check it, and if it is a bug, we may send you a new version with a
bug fix. If perchance we found a bug or a trouble, we may send you a new version after we contact you.
When we send you the new version software, we may ask you to update software. Therefore, we strongly
recommended being able to access to serial port of this product from outside of your product to make software
update easy. In addition, we also strongly recommend connecting between serial port of this product and
network to remote access and update software.
In this product, FURUNO can ensure safe performance only the commands and the sentences which are
written in this document or are written in the document for this product. Please do not use the commands of the
others products, otherwise this product may have troubles and FURUNO may not support about the troubles.
FURUNO may inform some internal commands for verification etc. In this case, please use the commands only
for operation test and please do not use them for technical operation.
FURUNO ELECTRIC CO., LTD. reserves the right to make changes to its products and specifications without
notice.
GT-88
Protocol Specifications
SE18-600-003-00
Revision History
Version
0
Changed contents
Initial release.
Date
2019.04.18
GT-88
Protocol Specifications
SE18-600-003-00
Table of Contents
1
2
3
4
Outline ······················································································································ 1
Terms ························································································································ 1
Communication Specifications ··················································································· 10
Serial Data Output Timing ·························································································· 11
4.1
Output Timing of 1PPS and Serial Data ·········································································· 11
4.2
Notes on Sentence Output ···························································································· 11
5 NMEA Sentence Format ····························································································· 12
5.1
Standard Sentence ······································································································ 12
5.2
Proprietary Sentence ··································································································· 13
5.3
Talker ID ····················································································································· 14
5.4
Output Priority of Sentence and Default Output Sentence ················································ 15
6 Output Sentences ····································································································· 16
6.1
RMC – Recommended Minimum Navigation Information ·················································· 16
6.2
GNS – GNSS Fix Data ··································································································· 17
6.3
GGA – Global Positioning System Fix Data ····································································· 18
6.4
GLL – Geographic Position - Latitude/Longitude ····························································· 19
6.5
VTG – Course Over Ground and Ground Speed ······························································· 20
6.6
GSA – GNSS DOP and Active Satellites ·········································································· 21
6.7
ZDA – Time & Date ······································································································· 22
6.8
GSV – GNSS Satellites in View ······················································································ 23
6.9
QSM – Satellite Report for Disaster and Crisis Management (DC Report) Message ·············· 25
6.10 CRW (TPS1) – Time and Leap Second ············································································ 26
6.11 CRX (TPS2) – PPS Information ······················································································ 28
6.12 CRY (TPS3) – Position Mode & TRAIM ············································································ 30
6.13 CRZ (TPS4) – GCLK Frequency and Control ··································································· 33
6.14 CRG – QZSS L1S Disaster and Crisis Management Report Message·································· 35
6.15 CRJ – Detection Status of Jamming Signal ····································································· 36
6.16 CRP – High Resolution Current Position········································································· 37
6.17 CRQ – SAR / RLM Information Broadcasted by Galileo Satellites ······································ 38
6.18 ACK – Output the Command Reception Check ································································ 39
6.19 MSG – Event Driven Message························································································ 39
6.20 VERSION – Software Version ························································································ 40
6.21 GPIO – General Purpose Input / Output ·········································································· 40
6.22 FIXSESSION – Fix Session···························································································· 41
6.23 ANTSEL – Antenna Selecting ························································································ 41
7 Input Commands ······································································································ 42
7.1
API [GNSS] – Satellite System Configuration ·································································· 42
7.2
API [PPS] – PPS Setting ······························································································· 43
7.3
API [FREQ] – GCLK Frequency Setting··········································································· 44
7.4
API [SURVEY] – Position Mode Setting··········································································· 45
7.5
API [RESTART] – Restart Command··············································································· 47
7.6
API [FLASHBACKUP] – Back up to FLASH ROM ····························································· 48
7.7
API [DEFLS] – Default Leap Second Setting ···································································· 49
7.8
API [TIMEZONE] – Local Zone Time Setting ···································································· 50
7.9
API [TIMEALIGN] – Time and PPS Alignment Setting ······················································· 52
7.10 API [TIME] – Time Setting ····························································································· 53
7.11 API [FIXMASK] – Positioning and Satellite Mask Setting··················································· 54
7.12 API [OCP] – Detailed Elevation and Azimuth Mask Setting ················································ 55
7.13 API [NLOSMASK] – NLOS Satellite Elimination Algorithm Setting ····································· 58
7.14 API [ECLK] – ECLK Mode Setting ·················································································· 60
7.15 API [ECLKCNT] – Measurement of ECLK pin frequency ··················································· 62
7.16 API [CROUT] – CR Sentence Output Setting ··································································· 63
7.17 CFG [NMEAOUT] – Standard NMEA Output Setting·························································· 64
7.18 CFG [UART1] – Serial Communication Port Setting ························································· 64
7.19 SYS [VERSION] – Software Version Request ··································································· 65
7.20 SYS [GPIO] – GPIO Output Request ··············································································· 65
GT-88
Protocol Specifications
SE18-600-003-00
7.21 SYS [ANTSEL] – Antenna Input Setting ·········································································· 66
8 Backup of the Receiver Parameters (for BBRAM) ·························································· 67
9 Insertion of Leap Second ··························································································· 69
10 Instructions and Directions for Use ············································································· 70
11 FAQ ························································································································ 71
GT-88
Protocol Specifications
SE18-600-003-00
1 Outline
This document describes the serial communications interface protocol (eSIP protocol) for GT-88.
The software version covered by this document is 4850-577-000 (ENP708A) or later.
2 Terms
This chapter describes details of terms used in this document.
Since it contains a lot of important information on the behavior of this product, we strongly recommend you to
read it carefully.
Terms
Protocol
Command
Sentence
Serial data
eSIP
PFEC
M12
National Marine
Electronics
Association (NMEA)
ACK
NACK
Table 2.1 Terms Related to Communication
Description
It is a communication procedure for sending and receiving data using the
communication port.
In this document, the data sent to the product is called a command.
In this document, the data received from the product is called a sentence.
It is a generic name of the data itself to transmit and receive using the
communication port. Although it may be described as output of serial data in this
document, in that case it is synonymous with sentence.
It is one of protocol format. It is the standard format output by our GNSS receiver.
This document mainly describes details about the eSIP.
It is one of protocol format. It is the format output by our past products (GT-80 etc.). If
you need details of this protocol, please contact us.
It is one of protocol format, and called Motorola Binary Protocol. If you need details of
this protocol, please contact us.
In this document, ASCII and communication protocol of NMEA 0183 standard are
called NMEA. The product outputs serial data conforming to NMEA0183 Ver. 4.10
established in June 2012.
It means acknowledgement. When a command is input to the product, if the
command is accepted as being appropriate, the product returns ACK as a response
sentence.
It means negative acknowledgement. When a command is input to the product, if the
command is ignored as being inappropriate, the product returns NACK as a
response sentence. If NACK is returned, please check whether the format of the
transmitted command is appropriate and checksum is appropriate.
1
GT-88
Protocol Specifications
SE18-600-003-00
Terms
Ephemeris
Table 2.2 Terms Related to Messages Broadcast by Satellites
Description
It is one of information that the satellite is broadcasting. Mainly satellite time and
detailed orbit information of its satellite are broadcasted. It is information necessary
for positioning, and it is repeatedly broadcast in short cycles. In case of GPS
satellites, the ephemeris is broadcasted every 30 seconds.
It is called HOT START especially in this product to start up with ephemeris
information remaining in the receiver.
Although the expiration date of the ephemeris it possesses depends on the type of
satellite, but it is 1 to 4 hours since the last ephemeris was received.
It is one of information that the satellite is broadcasting. Mainly various correction
information, UTC parameters and rough orbit information of all satellites are
broadcasted. In case of GPS satellites, the almanac is broadcasted at a cycle of 900
seconds. Therefore, it may take up to 900 seconds from GPS synchronization to
UTC synchronization after initial positioning.
Almanac
It is called WARM START especially in this product to start with almanac information
remaining in the receiver. If neither ephemeris nor almanac information remains in
the receiver, it will start by COLD START.
Interface Control
Document (ICD)
There is no expiration date for the almanac it possesses.
It is a document defining the content and structure broadcasted by each satellite as a
specification by the relevant division of the country that operates the satellites. This
product is designed based on those ICD. The ICD referred to by this product is as
follows.
Satellite
ICD
IS-GPS-200
GPS
Revision H,IRN003
28 July 2016
Navigation radiosignal In bands L1, L2
GLONASS
Version 5.1
2008
EUROPEAN GNSS(GALILEO) OPEN SERVICE
SIGNAL-IN-SPACE
Galileo
Issue 1 revision 3
December 2016
IS-QZSS-PNT-002
QZSS L1C/A
29 January 2018
IS-QZSS-L1S-002
QZSS L1S
13 April 2018
ICD does not claim permanent specification definition, so ICD of the satellite may be
updated in the future depending on the type of satellite, and a part of the broadcast
content may be changed. Please note that this product does not guarantee including
the changed part of those updated ICD.
2
GT-88
Protocol Specifications
SE18-600-003-00
Terms
GNSS (GNSS
satellite)
SBAS (Differential
correction)
SLAS correction
information
Satellite number
Jamming signal
Anti-Jamming
Spoofing signal
Table 2.3 Terms Related to Satellite and Satellite Signal
Description
GNSS stands for Global Navigation Satellite System. It may be described as a
generic name of satellites such as GPS, GLONASS, Galileo, QZSS and SBAS.
SBAS is a satellite transmitting correction information useful for positioning
calculations. This correction information is called differential information, and
correcting the positioning calculation process using this information is called
differential correction. This product supports differential correction and this is done
by default.
It is possible to add SBAS itself as one satellite to the positioning calculation like
GPS. However, experiments show that the positioning performance deteriorates
when SBAS is added to the positioning calculation. Therefore, in this product, SBAS
is set not to add to positioning calculation by default.
In our experiment, the order of contributing to performance improvement by using
SBAS is as follows: Use differential positioning only > Use differential positioning +
SBAS positioning > Do not use SBAS. In addition, since SBAS alone cannot align
parameters necessary for initial positioning, SBAS standalone positioning setting is
prohibited in this product.
It is correction information broadcasted from the QZSS L1S signal. It can be used
when QZSS L1S signal is received.
It is the number assigned to the satellite. In this product, the satellite number is
assigned as follows. These satellite numbers are mainly used for GSA and GSV.
(Please refer to the hardware specifications for satellite numbers that can be actually
received.)
Satellite
GPS
SBAS
GLONASS
QZSS L1C/A
QZSS L1S
Galileo
MIN
01
33
65
93
83
01
MAX
32
51
96
99
89
36
Notes
Same as PRN No
Sabtract 87 from PRN No
Same as PRN No
Sabtract 100 from PRN No
Sabtract 100 from PRN No
Same as PRN No
When the satellite number is duplicated, the type of satellite can be distinguished by
the GNSS system ID of GSA sentence or the talker ID of GSV sentence.
It is a signal other than the satellite signal that is mixed in the frequency band of the
satellite signal. Noises of other equipment may accidentally be mixed in, or
intentional broadcasting by malicious persons may be mixed. If the jamming signal is
received, it will be impossible to receive the frequency of the satellite signal, resulting
in a poor positioning or undetectable state.
Even if a jamming signal is mixed in, the receiver masks the signal as much as
possible so that it can receive satellite signals normally. In this product, the
Anti-Jamming function is operating by default, and it is possible to mask up to eight
jamming signals.
It is a signal generated by a malicious person mimicking the broadcast contents of
GNSS satellite using what is similar to simulator. Reception of this signal may affect
the position and time. This product has a function to detect and eliminate spoofing
signal. For details, please refer to TPS3 sentence.
3
GT-88
Protocol Specifications
SE18-600-003-00
Terms
Leap second
Table 2.4 Terms Related to Time
Description
It means one second that is inserted so that there is no gap in the difference between
the rotation of the earth and the atomic clock that is the time reference. Normally, the
leap second insertion is determined, announced, and broadcasted one to two
months in advance. Insertion timing is January 1st or July 1st.
The leap second has been inserted since 1972. However, considering that GPS and
QZSS satellites are being operated starting from January 6, 1980, this product
displays the leap second integrated value since January 6, 1980. This is consistent
with the integrated value of leap second that the GPS, QZSS and Galileo satellite
actually broadcast as a message.
In this document, the integrated value of leap second may be referred to simply as
leap second.
It is time system broadcasted by GPS satellite. It is broadcasted as a continuous
time that does not consider the leap second since the start of January 6, 1980.
GPS time
GPS satellites broadcast the week number (0 to 1023) and the week second (0 to
640799). The receiver converts to the current time by using them.
In recent years the time difference between UTC time and GPS time is on the order
of a few nanoseconds. However, there is no guarantee that this time difference will
be kept for the future.
The week number broadcasted by the GPS and QZSS satellite returns to 0 the next
week of 1023. Therefore, if only these satellites are being received, it is known that
there is a limit in the period during which the current time can be properly converted
by a general GNSS receiver. In this document, the timing at which week number
1023 goes to 0 is called week number rollover.
Week number rollover
GLONASS time
This product addresses to this week number rollover, and even if the broadcasted
week number returns to 0 from 1023, the correct time can be displayed continuously.
However, the time range that can be converted properly is still up to 1024 weeks.
The range in which this product can display an appropriate time without backup is up
to 23:59:59 on October 10, 2037. If the receiver starts and restarts without backup
after then, the time before 1024 weeks may be displayed. In this case, you can
display the correct time by setting the correct time with the command or by
positioning with the GLONASS satellite or Galileo satellite. If the power is on
continuously, the time update can be continued appropriately even if it exceeds the
above date.
It is time system broadcasted by GLONASS satellite. It is a time that always
considered leap second, starting from January 1, 1996. Time parameters that can be
uniquely converted until 2100 or later are broadcasted. By receiving the GLONASS
satellite, it is possible to display the correct time without being conscious of week
number rollover that was concerned with receiving only GPS and QZSS satellites.
Also, because it includes leap seconds in the time system, by receiving the
GLONASS satellite and other satellites at the same time, it is possible to immediately
acquire the correct leap second without waiting for the reception of the UTC
parameter.
4
GT-88
Protocol Specifications
SE18-600-003-00
Terms
Galileo time
UTC time
UTC parameter
Default leap second
Local Zone Time
(LZT)
Estimated accuracy
Table 2.5 Terms Related to Time
Description
It is time system broadcasted by Galileo satellite. It starts from August 22, 1999.
However, practically it is broadcasted as a continuous time that does not consider
the leap second since January 6, 1980, so that each parameter matches the GPS
and QZSS satellite. Time parameters that can be uniquely converted until February
19, 2078 are broadcasted. By receiving the Galileo satellite, it is possible to display
the correct time until 2078 without being conscious of the week number rollover that
was concerned with receiving only GPS and QZSS satellites.
UTC stands for Coordinated Universal Time.
It is always considered leap second and matches the time we usually use by
considering the time difference of each country. UTC is set for each country by the
atomic clock owned by each country, and it is slightly different on the nanosecond
scale although it cannot see any difference in any country over integer seconds.
For example, in case of the United States, the United States Naval Observatory
prescribes the UTC time as UTC (USNO). Similarly, in case of Russia it is called
UTC (SU). This product can select which UTC to synchronize by command. The
default is synchronized to UTC (USNO).
It is a parameter broadcasted by each satellite to convert the time system of each
satellite to UTC time. Mainly it includes integrated value of leap second, leap second
insertion timing and correction information of nanosecond scale. However, since the
GLONASS satellite contains leap seconds in the time system, the accumulated value
of the leap second is not broadcasted.
The UTC parameters are generally included in navigation messages called almanac,
and there is a gap in the broadcasting interval.
This value is set to temporarily bring the sentence output time closer to the UTC time
when the leap second information has not been acquired from the GPS satellite. This
value can also be stored in FLASH ROM. By setting this properly in advance, it is
possible to get the time information equivalent to the UTC time earlier from the
sentence before acquiring the UTC parameter.
Note that this setting only adjusts the display time before acquiring the correct leap
second, and even if this value is incorrect it does not affect positioning calculation.
Also, if leap second information can be obtained from the satellite at least once, it will
be used with priority thereafter.
It means time offset value from UTC time. By setting the LZT with the TIMEZONE
command, you can obtain the time information with LZT added from the ZDA
sentence.
It shows how far the receiver's time may deviate from the synchronization target. The
standard deviation (1 sigma) of the pseudorange of all satellites displayed in the
GSA sentence is displayed in nanoseconds.
In an open sky environment, this value will be lower. In poor environments such as
indoors, this value will increase due to the influence of multipath satellites. Therefore,
it can be used to judge whether the reception environment is good or bad.
For explanation of pseudorange and multipath, please refer to the following.
5
GT-88
Protocol Specifications
SE18-600-003-00
Terms
Pulse Per Second
(PPS)
GCLK frequency
LEGACY PPS
Table 2.6 Terms Related to PPS and Frequency
Description
Outputting one pulse per second is called 1PPS, and outputting one pulse per 2
seconds is called PP2S.
It is a mechanism to generate arbitrary frequency by using the system clock of this
product and built-in adder. By receiving the GNSS satellite, it is possible to output
arbitrary frequency accurately. Since the frequency is generated using the adder, it is
necessary to check in advance whether jitter and spurious included in the GCLK
frequency are within the allowable range of the application to be used.
It is a normal PPS type. This is the default state. Please use this PPS type if there is
no particular reason. By receiving the GNSS satellite, the PPS will be synchronized
and output properly at the timing when the UTC parameter and time are fixed.
It is a PPS type to be used when synchronizing the timing of the clock edge of GCLK
frequency and the pulse edge of PPS using the GCLK frequency. The PPS is
generated by dividing the GCLK frequency by the internal frequency divider.
GCLK PPS
Holdover
Cable delay
Quantization error
RTC synchronization
GPS synchronization
UTC synchronization
Since it is necessary to control both the GCLK frequency and GCLK PPS at the
same time, it may take several minutes to synchronize PPS as compared with
LEGACY PPS. Also, accuracy may slightly deteriorate compared to LEGACY PPS.
It is a function to maintain the performance of 1PPS and frequency during satellite
reception as much as possible while GNSS satellites cannot be received.
When connecting the antenna and this product with a cable, a delay occurs in PPS
according to the cable length. In this document, this delay is called cable delay. This
delay can be corrected with the PPS command.
General GNSS receivers can obtain the calculation result of time with extremely high
resolution when performing position calculation internally. However, when outputting
it as PPS with the PPS port, it is known that the resolution is limited depending on the
clock installed in the product. The error of PPS caused by this resolution limitation is
called quantization error in this document. Although this product makes this
quantization error extremely small, if you want to remove this error furthermore, you
can correct it to picoseconds by using the sawtooth field of TPS2 sentence.
RTC stands for Real Time Clock.
It is sometimes described as RTC synchronization especially in this document to
indicate that the PPS and frequency are in free-run state before receiving the
satellite and confirming the time, or when GNSS interruption continues for more than
a certain period of time.
It is a state outputting the time, PPS and frequency in synchronization with the GPS
time. This product transits to this state when GPS synchronization is set or UTC
parameter is not acquired.
It is a state outputting the time, PPS and frequency in synchronization with the UTC
time. User can select to which UTC to synchronize by a command.
6
GT-88
Protocol Specifications
SE18-600-003-00
Terms
Frequency mode
ECLK mode
WARMUP
PULLIN
LOCK
FREERUN
ECLK_LOCK
ECLK_HOLDOVER
ECLK_FREERUN
Terms
Battery Backup
Random Access
Memory
(BBRAM)
FLASH ROM
(FLASH)
Table 2.7 Terms Related to PPS and Frequency
Description
It mainly shows the stable state of the GCLK frequency. It may show the stable state
of PPS and GCLK frequency when using the ECLK pin. There are seven kinds of
frequency modes: WARMUP, PULLIN, LOCK, FREERUN, ECLK_LOCK,
ECLK_HOLDOVER, and ECLK_FREERUN.
It is a mode in which holdover is possible. This mode can be used by connecting an
oscillator to the ECLK pin and inputting the ECLK command. For details, see the
ECLK command chapter.
It is a state waiting for stabilization of the internal clock after turning on the power
supply.
It is in the middle of synchronizing the GCLK frequency and GCLK PPS with the
synchronization target.
It is a state that the GCLK frequency and GCLK PPS are synchronized with the
synchronization target.
It is a state that GNSS cannot be received and the GCLK frequency and GCLK PPS
are free-running.
It is in ECLK mode and receiving satellite.
It is in ECLK mode and in holdover state of GCLK frequency and LEGACY PPS by
using the oscillator connected to the ECLK pin when satellite interruption occurs.
It is in ECLK mode, and satellite interruption occurs and the condition of holdover is
not satisfied.
Table 2.8 Terms Related to Storage Area
Description
It is a storage area that can be used as a backup area only when backup current is
applied to this product. Ephemeris data, almanac data, command setting values and
so on are sequentially stored.
The storage area is read at startup or at restart. You can erase the stored information
by interrupting the application of backup current or sending a prescribed reset
command to this product.
It is a storage area using Flash ROM. By sending FLASHBACKUP command to this
product, some settings can be saved at that timing.
The storage area is read at startup or at restart. Once backed up to FLASH, it can be
eraced only when software update or FLASHBACKUP command is sent again.
When settings related to the same item are stored in both BBRAM and FLASH,
BBRAM setting takes precedence. At this time, if the data on the BBRAM side
becomes invalid due to stoppage of backup power supply, FLASH data will be
applied at the next start or restart.
7
GT-88
Protocol Specifications
SE18-600-003-00
Terms
Time Receiver
Autonomous Integrity
Monitoring
(T-RAIM)
Position mode
Fixed position
Estimated position
(Position estimation)
NAV mode
(Navigation)
TO mode
(Time Only)
SS mode
(Self Survey)
CSS mode
(Continuous Self
Survey)
Table 2.9 Terms Related to Positioning Processing
Description
It is a mechanism to identify and eliminate satellites that may have a bad influence
on the positioning calculation by combining and principle of majority when the
number of satellites in use is larger than the minimum number of satellites required
for positioning. With this function, the results of the positioning calculation are further
improved. The maximum number of satellites eliminated by this function is 3.
Generally, the GNSS receiver calculates parameters such as latitude, longitude,
height, speed, direction and time by receiving four or more satellites. On the other
hand, if it is known in advance to use the receiver at a fixed position, by preparing the
latitude, longitude and height in advance, the time can be calculated with only one or
more satellite reception, precise 1PPS and frequency can be maintained.
There are four kinds of position mode: NAV mode, TO mode, SS mode and CSS
mode.
The position of the fixed point to be set when using the TO mode may be described
like this in this document.
In the process of calculating the fixed position, the position that the position accuracy
is not sufficiently converged yet may be described as the estimated position in this
document. In addition, the process of calculating the estimated position may be
described to as position estimation.
Latitude, longitude, height, speed, direction and time are calculated every second.
Since position, speed and direction are updated every second, it is suitable for
mobile use. In order to perform positioning in this mode, it is required to receive four
or more satellites except SBAS.
By using the fixed position, only time is calculated every second. Compared to NAV
mode, it is excellent in time stability and it is suitable for use at fixed points. In order
to perform positioning in this mode, it is required to receive one or more satellites
except SBAS.
Latitude, longitude, height and time are calculated every second. This mode is
suitable when you want to use the TO mode but you do not know the position of the
fixed point. This mode calculates the position of the fixed point with high accuracy
based on the position information obtained during a fixed period (default 24 hours),
and after calculating it transits to the TO mode automatically.
In order to calculate the fixed position in this mode, it is required to receive four or
more satellites except SBAS. However, even if it is less than four satellites, if there is
more than one satellite, processing equivalent to the TO mode is performed using
the information of the fixed position calculated so far, the time is appropriately
updated, precise 1PPS and frequency can be maintained.
Although processing similar to the SS mode is performed, while the SS mode
discards the calculation process of the fixed position when the power is off, the CSS
mode backs up the calculation process to the BBRAM. Therefore, the calculation of
the fixed position is continued using the calculation process before turning off the
power even at the next startup.
8
GT-88
Protocol Specifications
SE18-600-003-00
Terms
Positioning
calculation
Pseudorange
Doppler frequency
Line Of Sight
(LOS)
Table 2.10 Terms Related to Positioning Processing
Description
It means that the GNSS receiver calculates various kinds of information such as
satellite and receiver position, speed, time and receiver azimuth based on
information from the satellites.
It is one of the information used by the GNSS receiver at positioning calculation. It is
the result of calculating the distance between the satellite and the receiver.
It is one of the information used by the GNSS receiver at positioning calculation. It is
the result of calculating the frequency of the signal received from the satellite.
It means that a signal from a satellite is coming directly to the antenna connected to
this product. It is synonymous with the state where there is no shielding between the
satellite and the antenna, and the satellite in such state is called LOS satellite
especially in this document.
If many LOS satellites can be received, not only stable signal level can be expected
but also position accuracy and time accuracy can be obtained satisfactorily.
In contrast to LOS satellites, it means that there is some sort of obstruction between
a satellite and the antenna. Although satellites whose signals are completely
discontinued and determined as satellite discontinuities are also strictly included in
NLOS satellites, in this document they are simply described as satellite interruption
and shall not be described as NLOS satellites.
Non Line Of Sight
(NLOS)
In this document, we define the satellite as the NLOS satellite, which cannot receive
the direct signal from the satellite but only weak signals that arrive bypassing by
reflecting to the surrounding building. Signals that are reflected to surrounding
buildings and are received bypassing are particularly called multipath. It is known
that using this multipath signal tends to degrade the positioning accuracy because
errors are generated in the calculation of pseudorange and Doppler frequency.
Determinating appropriately what satellite is the NLOS satellite and appropriately
masking them and performing positioning with only the LOS satellite leads to an
improvement in positioning accuracy.
9
GT-88
Protocol Specifications
SE18-600-003-00
3 Communication Specifications
Signal Lines used:
Flow Control:
System:
Speed:
Start Bit:
Data Length:
Stop Bit:
Parity Bit:
Data Output Interval:
Character Codes used:
TXD, RXD
None
Full Duplex Asynchronous
38400 bps [*1]
1 bit
8 bits
1 bit
None
1 second
NMEA-0183 Ver.4.10 data based ASCII code [*2]
Protocol:
Input data
NMEA Proprietary sentence
Output data
NMEA Standard sentence
NMEA Proprietary sentence
Notes:
[*1] Baud rate
It can be changed by a command. Please see UART1 command page for details. For the relationship between
UART baud rate and error, please refer to the hardware specifications.
[*2] NMEA format
“NMEA 0183 STANDARD FOR INTERFACING MARINE ELECTRONIC DEVICES Version 4.10” (NATIONAL
MARINE ELECTRONICS ASSOCIATION, June, 2012)
10
GT-88
Protocol Specifications
SE18-600-003-00
4 Serial Data Output Timing
4.1
Output Timing of 1PPS and Serial Data
The output timing of sentence (serial data) is synchronized with 1PPS output from PPS port after the time fix
by GNSS positioning. In the default state, the sentence output begins in the range from 25 ms to 75 ms after
the rising of 1PPS.
The time of the sentence indicates the time of the next 1PPS output timing. However, information and status
related to positioning other than time information are generated based on the positioning results one second
before.
Time = t
Time = t + 1
Time = t + 2
Reference Time
1PPS
Serial data
Time = t + 1
Time = t + 2
25 - 75 ms
25 - 75 ms
25 - 75 ms
Figure 4.1 Relation between 1PPS, Serial Data and Output Time
This relationship can be changed with the TIMEZONE command. For details, refer to the TIMEZONE
command chapter.
4.2
Notes on Sentence Output
This product limits the amount of sentences that can be outputted per second in order to maintain the output
relation between 1PPS and sentence. Sentence output per second is set to 90% of the number of bytes that
can be output at the current baud rate. Specifically, it is defined by the following calculation formula.
Maximum amount that can be output per second [Byte] = Current baud rate [bps] / 10 [Bit] *0.9
Therefore, when the baud rate is 38400 bps, it is possible to output up to 3456 bytes, but if you set it beyond
that, the sentence after the line considered to exceed it will be discarded without being output. When outputting
a large number of sentences, it is recommended to change to a higher baud rate by UART1 command.
11
GT-88
Protocol Specifications
SE18-600-003-00
5 NMEA Sentence Format
5.1
Standard Sentence
Format:
$
,
・・・
*
5 bytes
Field
$
Description
Start-of Sentence marker
5-byte fixed length. First 2 bytes represent a talker ID, and the remaining 3 bytes
represent the sentence data type.
The relevant talker IDs are GP for GPS, GN for GNSS, GL for GLONASS and GA
for Galileo. See Section 5.3 for details of talker ID.
Variable or fixed-length fields preceded by delimiter “,” (comma).
Comma(s) are required even when valid field data is not available i.e. null fields.
Ex. “,,,,,”
*
In a numeric field with fixed field length, fill unused leading digits with zeroes.
8 bits data between “$” and “*” (excluding “$” and “*”) are XORed, and the resultant
value is converted to 2 bytes of hexadecimal letters. Note that two hexadecimal
letters must be preceded by “*”, and delimiter “,” is not required before
*.
All output sentences have checksum.
For input sentences, the resultant value is checked and if it is not correct, the
sentence is treated invalid.
End-of-Sentence marker
12
GT-88
Protocol Specifications
SE18-600-003-00
5.2
Proprietary Sentence
Format:
$
P
3 bytes
,
*
*
3 bytes
Field
$
P
・・・
Description
Start-of Sentence marker
Proprietary sentence identifier
3-byte fixed length.
Maker ID of this product is “ERD” meaning eRide.
Indicates the type of sentence. There are three types: API type, CFG type, SYS
type.
Variable or fixed-length fields preceded by delimiter “,”(comma).
(Layout is maker-definable.)
The fields inside [ ] are optional fields.
8 bits data between “$” and “*” (excluding “$” and “*”) are XORed, and the resultant
value is converted to 2 bytes of hexadecimal letters. Note that two hexadecimal
letters must be preceded by “*”, and delimiter “,” is not required before
*.
All output sentences have checksum.
For input sentences, the resultant value is checked and if it is not correct, the
sentence is treated invalid.
End-of-Sentence marker
13
GT-88
Protocol Specifications
SE18-600-003-00
5.3
Talker ID
The talker ID displayed in the standard NMEA format changes as shown in Table 5.1, depending on the type of
satellite being received and the talker ID field of the GNSS command.
In this chapter, in the following chapters, the talker ID part is expressed as "XX" indicating a wild card.
Table 5.1 Talker ID Displayed in Standard NMEA Format
Talker ID setting
Standard NMEA
AUTO
GN
LEGACYGP
RMC
GNS
GGA
GN
GLL
GN/GP/GL/GA [*1]
GP [*2]
VTG
ZDA
GSA
GN/GP/GL/GA [*1]
GSV
GP/GL/GA [*3]
GP/GL/GA [*4]
[*1]
GN/GP/GL/GA switches according to the type of satellite used in positioning as follows.
GN: Multi satellite system is available [*5], or no position fix.
GP: Only GPS/QZSS/SBAS is used in position fix.
GL: Only GLONASS is used in position fix.
GA: Only Galileo is used in position fix.
[*2]
Even if it is set to use GLONASS or Galileo, and even if it is actually received, GSA and GSV will be displayed
only in GP, and GSA / GSV information of GLONASS and Galileo will not be displayed. However, these
satellites are not actually displayed, they are actually counted by the number of positioning satellites of GNS
and GGA, and used in positioning calculations, various status calculations and displays.
[*3]
GP/GL/GA switches according to the type of satellite used in positioning as follows.
GP is displayed while no positioning fix, receiving GPS/QZSS/SBAS, or receiving multi satellite system
[*5].
GL is displayed while no positioning fix, receiving GLONASS, or receiving multi satellite system [*5].
GA is displayed while no positioning fix, receiving Galileo, or receiving multi satellite system [*5].
[*4]
The GPGSV, GLGSV, and GAGSV sentences are always output to maintain the display form of the sentence
even if it is no position fix or it cannot receive the satellite corresponding to the talker ID.
[*5]
The multi satellite system means a state that two or more groups are received from the combination of groups
"GPS/QZSS/SBAS", "GLONASS", and "Galileo".Therefore, for example, even if GPS and QZSS are received,
only GPGSV will be displayed as it is only receiving "GPS/QZSS/SBAS" group. Meanwhile, for example, when
GPS and GLONASS are received, GAGSV is also displayed even if Galileo is not received because it satisfies
the condition that it is receiving multiple kinds of satellites.
14
GT-88
Protocol Specifications
SE18-600-003-00
5.4
Output Priority of Sentence and Default Output Sentence
Sentences are output in the order shown in Table 5.2. Table 5.2 also shows the sentences that are output by
default. They are output every second. Sentence output switching is possible with the CROUT command and
the NMEAOUT command.
Table 5.2 Output Priority of Sentence and Default Output Sentence
Output priority
Sentence
Default output
Setting command
RMC
●
GNS
●
GGA
GLL
VTG
NMEAOUT
GSA
●
High
ZDA
●
GSV
●
QSM
CRG
CRJ
CRP
Low
CRQ
CROUT
CRW(TPS1)
●
CRX(TPS2)
●
CRY(TPS3)
●
CRZ(TPS4)
●
QUERY
Each command
15
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Protocol Specifications
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6 Output Sentences
This chapter describes details of sentences output from GT-88. There are unsupported fields in the output
sentences. This document shows these fields as “NULL”. These fields are null fields.
6.1
RMC – Recommended Minimum Navigation Information
Format:
$XXRMC , hhmmss.sss , a , ddmm.mmmm , a , dddmm.mmmm , a , x.xx ,
1
2
3
4
5
x.xx , ddmmyy ,
8
9
Field
Data
Range
Default
1
Time
000000.000 to
235960.000
-
2
Status
A, V
V
3
Latitude
0000.0000 to
9000.0000
ALL 0
4
Latitude
direction
N, S
N
5
Longitude
00000.0000 to
18000.0000
ALL 0
E, W
E
-
0.00
,
10
,
11
*hh
13
ddd: [degree], mm.mmmm: [minute]
True course
0.00 to 359.99
0.00
9
Date
010100 to
311299
-
NULL
NULL
Always NULL
NULL
NULL
Always NULL
11
12
V
"N" (North) or "S" (South)
8
Magnetic
declination
Magnetic
direction
,
dd: [degree], mm.mmmm: [minute]
7
10
a
7
Description
It is output at RTC, GPS, UTC time according to
positioning status, synchronization setting status,
parameter acquisition status and so on.
60 seconds is displayed only when the leap is
inserted.
A: Data valid
V: Data invalid
Longitude
direction
Speed
6
6
"E" (East) or "W" (West)
[knot]
[degree]
Variable length
dd: [day], mm: [month], yy: [year] (last two digits)
12
Positioning
mode
A, D, N
N
A: GNSS fix
D: Differential GNSS fix
N: No position fix
13
Navigation
status
V
V
Always “V”
Example:
$GNRMC,012344.000,A,3442.8266,N,13520.1233,E,0.00,0.00,191132,,,D,V*0B
Time: 01:23:44.000 Data valid 34 deg 42.8266 min N 135 deg 20.1233 min E
True Course: 0.0 degrees Date: 19th November, 2032 Differential GNSS fix
16
Speed: 0.0 knots
GT-88
Protocol Specifications
SE18-600-003-00
6.2
GNS – GNSS Fix Data
Format:
$XXGNS , hhmmss.sss , ddmm.mmmm , a , dddmm.mmmm , a , ccc , xx ,
1
2
3
x.x
,
8
x.x
,
9
Field
Data
Range
Default
1
Time
000000.000 to
235960.000
-
2
Latitude
0000.0000 to
9000.0000
ALL 0
3
Latitude
direction
N, S
N
4
Longitude
00000.0000 to
18000.0000
ALL 0
5
Longitude
direction
E, W
E
6
Positioning
status
NNN to DDD
(A,D,N)
NNN
7
Number of
satellites in use
00 to 32
00
8
HDOP
0.0 to 50.0
or NULL
NULL
9
Sea-level
altitude
-
-18.0
10
Geoidal height
-
18.0
11
12
DGPS time
DGPS number
Navigation
status
NULL
NULL
NULL
NULL
V
V
13
4
x.x
5
,
10
6
,
11
,
12
7
V
*hh
13
Description
It is output at RTC, GPS, UTC time according to
positioning status, synchronization setting status,
parameter acquisition status and so on.
60 seconds is displayed only when the leap is
inserted.
Latitude
dd: [degree], mm.mmmm: [minute]
"N" (North) or "S" (South)
Longitude
ddd: [degree], mm.mmmm: [minute]
"E" (East) or "W" (West)
Positioning status for each satellite system
(GPS, GLONASS, Galileo)
A: GNSS fix
D: Differential GNSS fix
N: No position fix
Number of satellites in use
Horizontal dilution of precision (HDOP)
Variable length
A null field is output while positioning is interrupted.
[meter]
Variable length
[meter]
Variable length
Always NULL
Always NULL
Always “V”
Example:
$GNGNS,004457.000,3442.8266,N,13520.1235,E,DDN,22,0.5,40.6,36.7,,,V*60
Time: 00:44:57.000 34 deg 42.8266 min N 135 deg 20.1235 min E
Status: [GPS: Differential GNSS fix, GLONASS: Differential GNSS fix, Galileo: No position fix]
Number of satellites: 22 satellites HDOP: 0.5 Altitude: 40.6 meters high
Geoidal height: 36.7 meters high Navigation status indicator: Not valid
17
GT-88
Protocol Specifications
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6.3
GGA – Global Positioning System Fix Data
Format:
$XXGGA , hhmmss.sss , ddmm.mmmm , a , dddmm.mmmm , a , x , xx ,
1
2
x.x
8
3
,
x.x
,
9
4
M
10
,
x.x
5
,
11
M
12
,
13
6
7
,
*hh
14
Field
Data
Range
Default
1
Time
000000.000 to
235960.000
-
2
Latitude
0000.0000 to
9000.0000
ALL 0
3
Latitude
direction
N, S
N
4
Longitude
00000.0000 to
18000.0000
ALL 0
5
Longitude
direction
E, W
E
"E" (East) or "W" (West)
6
Positioning
status
0 to 2
0
1: GNSS fix
2: Differential GNSS fix
0: No position fix
7
Number of
satellites in
use
00 to 12
00
Number of satellites in use [*1]
8
HDOP
0.0 to 50.0,
or NULL
NULL
-
-18.0
M
M
-
18.0
M
NULL
M
NULL
Horizontal dilution of precision (HDOP)
Variable length
A null field is output while positioning is interrupted.
[meter]
Variable length
Units of altitude, meters
[meter]
Variable length
Units of Geoidal height, meters
Always NULL
NULL
NULL
Always NULL
9
10
11
12
13
14
Sea-level
altitude
Unit
Geoidal
height
M
DGPS time
DGPS
number
Description
It is output at RTC, GPS, UTC time according to
positioning status, synchronization setting status,
parameter acquisition status and so on.
60 seconds is displayed only when the leap is
inserted.
Latitude
dd: [degree], mm.mmmm: [minute]
"N" (North) or "S" (South)
Longitude
ddd: [degree], mm.mmmm: [minute]
Example:
$GPGGA,025411.516,3442.8146,N,13520.1090,E,1,11,0.8,24.0,M,36.7,M,,*66
Time: 02:54:11.516 34 deg 42.8146 min N 135 deg 20.1090 min E Status: GNSS fix
Number of satellites: 11 satellites HDOP: 0.8 Altitude: 24.0 meters high
Geoidal height: 36.7 meters high
[*1]
GPS, SBAS, QZSS only. GLONASS and Galileo is not counted. The upper limit is 12.
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6.4
GLL – Geographic Position - Latitude/Longitude
Format:
$XXGLL , ddmm.mmmm , a , dddmm.mmmm , a , hhmmss.sss , a , a
1
Field
Data
1
Latitude
2
2
3
Range
0000.0000 to
9000.0000
Default
Latitude
direction
N, S
N
3
Longitude
00000.0000 to
18000.0000
ALL 0
4
Longitude
direction
E, W
E
5
Time
000000.000 to
235960.000
-
6
Status
A, V
V
7
Positioning
mode
A, D, N
N
ALL 0
4
5
6
*hh
7
Description
Latitude
dd: [degree], mm.mmmm: [minute]
"N" (North) or "S" (South)
Longitude
ddd: [degree], mm.mmmm: [minute]
"E" (East) or "W" (West)
It is output at RTC, GPS, UTC time according to
positioning status, synchronization setting status,
parameter acquisition status and so on.
60 seconds is displayed only when the leap is inserted.
A: Data valid
V: Data invalid
A: GNSS fix
D: Differential GNSS fix
N: No position fix
Example:
$GPGLL,3442.8146,N,13520.1090,E,025411.516,A,A*5F
34 deg 42.8146 min N 135 deg 20.1090 min E Time: 02:54:11.516
Mode: GNSS fix
19
Status: Data valid
GT-88
Protocol Specifications
SE18-600-003-00
6.5
VTG – Course Over Ground and Ground Speed
Format:
$XXVTG ,
x.x
,
1
T
2
,
,
3
M
, x.xx ,
N
, x.xx ,
K
, a
4
5
6
7
8
9
Field
Data
Range
Default
1
True course
0.00 to 359.99
0.00
2
3
4
5
6
7
8
Unit
Magnetic direction
Unit
Speed
Unit
Speed
Unit
T
NULL
M
N
K
T
NULL
M
0.00
N
0.00
K
9
Positioning mode
A, D, N
N
Example:
$GNVTG,0.00,T,,M,0.00,N,0.00,K,D*26
True Course: 0.00 degree Speed: 0.00 kts, 0.00 km/h
20
*hh
Description
[degree]
Variable length
Unit of true course, "T" (True)
Always NULL
"M" (Magnetic direction)
Speed [knot]
"N" (knots)
Speed [km/h]
"K" (Kilo meters/ Hour)
A: GNSS fix
D: Differential GNSS fix
N: No position fix
Mode: Differential GNSS fix
GT-88
Protocol Specifications
SE18-600-003-00
6.6
GSA – GNSS DOP and Active Satellites
Format:
$XXGSA , A , a , xx ,
1
Field
1
2
Data
Operational
mode
3
・・・
, xx ,
x.x
4-13
14
15
,
x.x
,
16
x.x
17
,
x
18
Range
Default
A
A
2D/3D auto-switching mode
1: No fix
2: 2D fix
3: 3D fix
2
Positioning
mode
1~3
1
3-14
Satellite
numbers used
in positioning
01 to 99
NULL
15
PDOP
16
HDOP
17
VDOP
18
GNSS System
ID
0.0 to 50.0,
or NULL
0.0 to 50.0,
or NULL
0.0 to 50.0,
or NULL
1 to 3
NULL
NULL
NULL
-
*hh
Description
If it is less than 12 satellites, it is filled with NULL. [*1]
Variable length
A null field is output unless 3D-positioning is performed.
Variable length
A null field is output while positioning is interrupted.
Variable length
A null field is output unless 3D-positioning is performed.
It shows which satellite information this GSA sentence
is displaying.
1: GPS (involve SBAS and QZSS)
2: GLONASS
3: Galileo
Example:
$GNGSA,A,3,09,15,26,05,24,21,08,02,29,28,18,10,0.8,0.5,0.5,1*33
$GNGSA,A,3,79,69,68,84,85,80,70,83,,,,,0.8,0.5,0.5,2*30
Position fix mode: 3D fix PDOP: 0.8 HDOP: 0.5 VDOP: 0.5
Satellite used [GPS]: 09, 15, 26, 05, 24, 21, 08, 02, 29, 28, 18, 10
Satellite used [GLONASS]: 79, 69, 68, 84, 85, 80, 70, 83
[*1] Satellite numbers used in positioning
Please use the GNSS system ID in the GSA sentence to identify which satellite the satellite number to be used
belongs to. For example, if 01 is displayed in the satellite number of the GSA sentence and the GNSS system
ID is 1, it means that it is No.1 satellite of GPS. If the GNSS system ID is 3, it means that it is No.1 satellite of
Galileo.
For the convenience of outputting the satellite number to be used in correspondence with the GNSS system ID,
the GSA may display up to three lines; one line for GPS/QZSS/SBAS, one line for GLONASS, and one line for
Galileo. When multiple lines are displayed, it is displayed in the order of GPS/QZSS/SBAS > GLONASS >
Galileo. A GSA with GNSS system ID of 1 takes precedence over GPS > QZSS > SBAS.
Since this GSA sentence is compliant with NMEA ver 4.10 established in June 2012, up to 12 satellite numbers
can be displayed on one line of GSA. Therefore, even if more than 13 satellites are used, only 12 satellites will
be displayed. However, if you wish to cancel this restriction and display more satellite numbers to be used, you
can display it by entering the following EXTENDGSA command.
$PERDAPI,EXTENDGSA,num*hh
num: Number of satellites to be display (Range: 12 to 16, Default: 12)
For example, if the number of satellites to be displayed is set to 16 by using this command, the field of satellite
number will be extended from “3 to 14” to “3 to 18”. The fields of PDOP, HDOP, VDOP are shifted behind.
For the satellite number, please also refer to corresponding items in Chapter 2.
21
GT-88
Protocol Specifications
SE18-600-003-00
6.7
ZDA – Time & Date
Format:
$XXZDA , hhmmss.sss , xx , xx ,
1
2
xxxx
3
4
Field
Data
Range
Default
1
Time
000000.000 to
235960.000
-
2
3
4
Day
Month
Year
Local zone
time [hour]
Local zone
time [minute]
01 to 31
01 to 12
1999 to 2099
-
-23 to +23
+00
00 to 59
00
5
6
, xxx , xx
5
*hh
6
Description
It is output at RTC, GPS, UTC time according to
positioning status, synchronization setting status,
parameter acquisition status and so on.
60 seconds is displayed only when the leap is inserted.
When LZT is set, time will be displayed after adding it.
When LZT is set, it will be displayed after adding LZT.
When LZT is set, it will be displayed after adding LZT.
When LZT is set, it will be displayed after adding LZT.
The LZT value set by the TIMEZONE command is
displayed. The unit is hour.
The LZT value set by the TIMEZONE command is
displayed. The unit is minute.
Example:
$GPZDA,014811.000,13,09,2021,+09,00*73
Time: 01:48:11 13th September, 2021
Local zone time: +9 hours
22
GT-88
Protocol Specifications
SE18-600-003-00
6.8
GSV – GNSS Satellites in View
Format:
$XXGSV , x , x , xx , xx , xx , xxx , xx , xx , xx , xxx , xx ,
1
Field
2
3
7
8
9
10
12
20
13
20
Signal ID
3
6
h
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
2
5
xx , xx , xxx , xx , xx , xx , xxx , xx ,
Data
Total number of
messages
Message number
Number of satellites
in line-of-sight
Satellite number
Elevation
Azimuth
C/N0
Satellite number
Elevation
Azimuth
C/N0
Satellite number
Elevation
Azimuth
C/N0
Satellite number
Elevation
Azimuth
C/N0
1
4
14
15
16
17
18
19
11
*hh
Range
Default
Description
1 to 5
1
Total number of messages per talker ID
1 to 5
1
Message number per talker ID
00 to 16
0
Number of satellites in line-of-sight per talker ID
01 to 99
00 to 90
000 to 359
00 to 69
01 to 99
00 to 90
000 to 359
00 to 69
01 to 99
00 to 90
000 to 359
00 to 69
01 to 99
00 to 90
000 to 359
00 to 69
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
NULL
1 or 7
-
1st satellite satellite number
1st satellite elevation angle [degree]
1st satellite azimuth angle [degree]
1st satellite C/N0 [dB-Hz]
2nd satellite details
Output in the same format as the first one.
3rd satellite details
Output in the same format as the first one.
4th satellite details
Output in the same format as the first one.
1: GPGSV or GLGSV
7: GAGSV
Example:
$GPGSV,4,1,14,15,67,319,52,09,63,068,53,26,45,039,50,05,44,104,49,1*6E
$GPGSV,4,2,14,24,42,196,47,21,34,302,46,18,12,305,43,28,11,067,41,1*68
$GPGSV,4,3,14,08,07,035,38,29,04,237,39,02,02,161,40,50,47,163,44,1*67
$GPGSV,4,4,14,42,48,171,44,93,65,191,48,,,,,,,,,1*60
$GLGSV,3,1,09,79,66,099,50,69,55,019,53,80,33,176,46,68,28,088,45,1*76
$GLGSV,3,2,09,70,25,315,46,78,24,031,42,85,18,293,44,84,16,246,41,1*7A
$GLGSV,3,3,09,86,02,338,,,,,,,,,,,,,,1*45
Not fixed
23
GT-88
Protocol Specifications
SE18-600-003-00
[Note]
The GSV sentence outputs up to four satellite information per line. More than four satellite information is output
to the second and subsequent messages. Conversely, if less than a multiple of 4 or there are items that are not
fixed in the satellite information, the item is NULL.
The satellite information of GPS/QZSS/SBAS is GPGSV, the satellite information of GLONASS is GLGSV, and
the satellite information of Galileo is output with GAGSV. The output order is GPGSV > GLGSV > GAGSV.
However, there are GSVs that are hidden depending on GNSS command setting and reception status. For
details, see about talker ID in Section 5.3.
In the GSV of the same talker ID, after satellite position calculation, in principle, satellites are displayed in order
of elevation angle. However, in the case of GPGSV, priority is given to GPS, QZSS and SBAS. In other words,
the display order is as follows: GPS high elevation angle > GPS low elevation angle > QZSS high elevation
angle > QZSS low elevation angle > SBAS high elevation angle > SBAS low elevation angle. However,
depending on the relation of search, and before satellite position calculation, that is not the limit.
When both QZSS L1C/A and QZSS L1S are used, the output order is QZSS L1S > QZSS L1C/A.
In case of setting to receive SBAS, the satellite number of SBAS may change gradually until SBAS first fix.
This shows the process of searching SBAS and will be resolved after receiving SBAS. Also, until the SBAS
position is calculated, 0 may be output temporarily in the elevation angle and azimuth fields of the SBAS, but
this will also be resolved after receiving the SBAS.
For the satellite number, please also refer to corresponding items in Chapter 2.
24
GT-88
Protocol Specifications
SE18-600-003-00
6.9
QSM – Satellite Report for Disaster and Crisis Management (DC Report) Message
QSM sentence is not a protocol of NMEA 4.1 support, but it is the output format recommended by NEC
operating and managing QZSS satellite to output DC report message.The output of DC report is also
supported by CRG sentence.
Format:
$QZQSM , Satellite ID , DC Report MSG *hh
1
Field
1
2
Data
Satellite ID
DC Report
MSG
2
Range
55, 56, 57, 58, 61
63 Bytes
(HEX)
Default
-
Description
Satellite number that received the DC report [*1]
DC report [*2]
[*1]
The satellite number is the lower 6 BIT in decimal notation of the 8 BIT which expresses the PRN number of
L1S in binary number. In other words, 55 means 183, 56 means 184, 57 means 185, 58 means 186, 61 means
189.
[*2]
In this field, "00" is added to the last 2 BIT of the 250 BIT DC report message and it is displayed with 252 BIT
(63 Bytes). Each BIT is represented by HEX and takes a range from 0 to F.
[Restrictions]
In order to properly output the DC report in this field, it is necessary to be set to receive the QZSS L1S signal
with the GNSS command. This sentence will not be output unless it is set to receive QZSS L1S signal.
This sentence outputs the information obtained by receiving the QZSS L1S signal as it is. The content of the
DC report message needs to be interpreted by the host based on the user interface specification of the Cabinet
Office. Please be aware that depending on the timing of message decoding, two different messages may be
output from the same satellite in one second.
Example:
$QZQSM,55,53AC12345……9ABCDEFC*1F
DC report “53AC12345……9ABCDEFC” is received.
25
GT-88
Protocol Specifications
SE18-600-003-00
6.10 CRW (TPS1) – Time and Leap Second
Format:
$PERDCRW , TPS1 , Date & Time , Time status , Update date , Present LS ,
1
2
3
4
5
Future LS , PPS status *hh
6
Field
1
Data
TPS1
Range
-
Default
-
2
Date & Time
(14 bytes)
-
3
Time status
0 to 2
(1 byte)
0
4
Update date
(14 bytes)
5
Present LS
6
Future LS
7
PPS status
-99 to +99
(3 bytes)
-99 to +99
(3 bytes)
0 to 5
(1 byte)
-
Description
Command name
Present date and time
year, month, day, hour, minute, second
It is output at RTC, GPS, UTC time according to
positioning status, synchronization setting status,
parameter acquisition status and so on.
60 seconds is displayed only when the leap is inserted.
Present time status of output sentence [*1]
0: Befor time fix
1: Leap second unknown or leap second ignored
2: Leap second fix
Leap second update schedule
year, month, day, hour, minute, second
It is filled with 0 when UTC parameter has not been
received or when there is no schedule for leap second
insertion even if it is received.
It is calculated based on satellite broadcast contents.
Therefore, the update date may remain displayed for a
while after the leap second insertion until the satellite
broadcast content changes.
+18
Present leap second [*2]
+00
Future leap second [*3]
0
7
Present PPS is synced with the follow. [*4]
0: RTC
1: GPS
2: UTC (USNO)
3: UTC (SU)
4: UTC (EU)
5: UTC (NICT)
Example:
$PERDCRW,TPS1,20120303062722,2,20120701000000,+15,+16,2*09
Present time: 2012/03/03 06:27:22
Present time status: UTC (leap second fix)
Leap second update date: 2012/7/1 00:00:00
Present leap second: +15
Future leap second: +16
PPS status: UTC(USNO)
26
GT-88
Protocol Specifications
SE18-600-003-00
[*1] Time status
Time status indicates the synchronization status of the time displayed in each sentence (including sentences
other than TPS1). It is useful for determining whether the sentence's output time is after the time information is
obtained from the satellite or contains an appropriate leap second.
I. 0: Befor time fix
The display time is incorrect since the time is not obtained from the satellites.
II.
1: Leap second unknown or leap second ignored
(1) "Ignore leap second" is selected with the TIMEALIGN command.
Time is displayed as GPS time. Leap second is not used.
(2) “Use leap second” is selected with the TIMEALIGN command.
Leap second has not been received from the satellites, and the time is displayed with the default leap
second.
III. 2: Leap second fix
Time is displayed as UTC time including the leap second.
[*2] Present leap second
This field shows the default leap second until information on leap second is obtained from the satellites. Also,
after the leap second information is obtained from the satellite, the information from the satellite is displayed as
it is. Therefore, when a leap second is inserted, even after insertion, the update date and the present LS fields
are not updated immediately, but are updated at the timing when the satellite actually updates the broadcast
contents (Usually within a few days after leap second insertion).
[*3] Future leap second
Like the AC field, this field also displays the information from the satellite as it is. Also, 0 is filled before UTC
parameter is received. Even if there is no schedule of leap second insertion, 0 may be displayed.
[*4] PPS status
PPS status indicates the synchronization status of PPS. It is useful for determining whether PPS is output at
the specified synchronization timing. It is different from the time status in that it shows the nanosecond scale
synchronization state below the integer seconds.
I.
0: RTC
The output PPS is not yet synchronized to anything. Even when the PPS status is GPS
synchronization or UTC synchronization, if satellite interruption occurs and it is determined that PPS
is largely out of synchronization target, RTC synchronization is displayed until re-positioning and time
fix.
II.
1: GPS
(1) “GPS synchronization” is selected with the TIMEALIGN command.
PPS is synchronized with GPS time.
(2) “UTC synchronization” is selected with the TIMEALIGN command.
The specified UTC parameter has not been received yet, it is provisionally synchronized with the GPS
time.
III. 2~5: UTC
It is synchronized with the UTC time set by the TIMEALIGN command. (The corresponding UTC
parameter has been received.)
27
GT-88
Protocol Specifications
SE18-600-003-00
6.11 CRX (TPS2) – PPS Information
Format:
$PERDCRX , TPS2 , PPS output , PPS mode , PPS period , Pulse width , Cable delay ,
1
2
3
4
Polarity , PPS type , Estimated accuracy ,
7
8
Sawtooth
9
Range
0, 1
(1 byte)
10
Field
1
Data
TPS2
2
PPS output
3
PPS mode
0 to 4
(1 byte)
3
4
PPS period
0, 1
(1 byte)
0
5
Pulse width
6
Cable
delay
7
Polarity
0, 1
(1 byte)
0
8
PPS type
0, 1
(1 byte)
0
9
Estimated
accuracy
0000 to 9999
(4 bytes)
9999
10
Sawtooth
-1.760 to +1.760
(6 bytes)
+0.000
11
PPS acc
threshold
0000 to 9999
(4 bytes)
0
001 to 500
(3 bytes)
-100000 to +100000
(7 bytes)
Default
0
5
, PPS acc threshold
*hh
11
Description
Command name
0: 1PPS OFF
1: 1PPS ON
Current PPS mode [*1]
0: Always stop
1: Always output
2: Output only when position and time fix
3: Output only when TRAIM is OK
4: Output only when estimated accuracy is less
than threshold
PPS output interval
0: 1PPS
1: PP2S
200
PPS pulse width [msec]
+000000
PPS cable delay [nsec]
PPS polarity
0: Rising edge
1: Falling edge
PPS type
0: LEGACY PPS
1: GCLK PPS
Displays the estimation accuracy of the GNSS
time being calculated. [*2]
For details of estimation accuracy, see the terms
in Chapter 2.
Correction value of PPS quantization error [nsec]
Correction is possible by adding this value to PPS
output 1 second before. For details of
quantization error, see the terms in Chapter 2.
Threshold of estimated accuracy [nsec]
It is used in PPS mode 4. 0 means that this
threshold is not used.
Example:
$PERDCRX,TPS2,1,2,0,200,+001000,0,0,0005,+0.354,1000*2B
PPS output : 1PPS ON
PPS mode: Output only when position and time fix
PPS period: 1PPS
Pulse width: 200 msec
Cable delay: +1000 nsec
Polarity: Rising edge
PPS type: LEGACY PPS
Estimated accuracy: 5 nsec
PPS acc threshold: 1000 nsec
28
6
GT-88
Protocol Specifications
SE18-600-003-00
[*1] PPS mode
When the PPS mode is 2, positioning is performed with more than 1 satellite in TO mode and 4 satellites or
more in NAV mode. In SS mode and CSS mode, more than 4 satellites are necessary to calculate the
estimated position, but even if it becomes 3 satellites or less, if it can receive more than 1 satellite, using the
estimated position so far, processing equivalent to TO mode is performed with the few satellites, and PPS that
is synchronized with the synchronization target is continuously output.
When the PPS mode is set to 3, PPS is output only when satisfying all the conditions of PPS mode 2 and using
the satellite that passed the TRAIM judgment. Reliability of PPS improves more than PPS mode 2.
[*2] Estimated accuracy
1 is always displayed when the frequency mode is HOLDOVER mode, 9999 is always displayed in FREERUN
mode. In the other frequency mode, it fluctuates according to the reception environment.
29
GT-88
Protocol Specifications
SE18-600-003-00
6.12 CRY (TPS3) – Position Mode & TRAIM
Format:
$PERDCRY , TPS3 , Pos mode , Pos diff , Sigma threshold , Time , Time threshold ,
1
2
3
4
5
6
TRAIM solution , TRAIM status , Removed SVs , Receiver status *hh
7
8
9
Field
1
Data
TPS3
Range
-
Default
-
2
Pos mode
0 to 3
(1 byte)
1
3
Pos diff
0000 to 9999
(4 byte)
1000
4
Sigma
threshold
000 to 255
(3 byte)
000
5
Time
000000 to 999999
(6 byte)
000000
6
Time threshold
000000 to 604800
(6 byte)
086400
7
TRAIM solution
0 to 2
(1 byte)
2
8
TRAIM status
0 to 2
(1 byte)
2
9
Removed SVs
10
Receiver status
00 to 03
(2 byte)
(10 byte)
00
0x00000000
10
Description
Command name
Positioning mode
0: NAV mode
1: SS mode
2: CSS mode
3: TO mode
Difference between the fixed position (or the
estimated position) and the calculated position
calculated by the positioning calculation in this
second. [meter] [*1]
Sigma threshold which changes automatically
to TO mode. [meter]
When the threshold value is 0, it is not used.
Current update times of estimated position
This value increments by 1 during 3D
positioning.
Survey time threshold which changes
automatically to TO mode.
When the threshold value is 0, it is not used.
TRAIM solution
0: OK
1: ALARM
2: Insufficient satellites being tracked
TRAIM status
0: There are enough number of satellites in
use
1: There are a number of satellites for alarm
determination
2: Not enough satellites
Number of satellites removed by TRAIM
Receiver status [*2]
Example:
$PERDCRY,TPS3,2,0003,001,002205,086400,0,0,00,0x00000001*69
Positioning mode: CSS mode
Position difference: 3 [m]
Sigma threshold: 1 [m]
Update times: 2205 times
Time threshold: 86400 times
TRAIM solution: OK
TRAIM status: There are enough number of satellites in use
Removed satellites: 0
Receiver status: 0x00000001 (Antenna short)
30
GT-88
Protocol Specifications
SE18-600-003-00
[*1] Reliability of fixed position
When the position mode is SS, CSS, TO mode, the Pos Diff field displays the difference between the fixed
position (or the estimated position created by integrating the position information for a certain period) and the
position obtained by positioning calculation at that time in meters per second. This value can be used as an
indicator of reliability of position information.
For example, if this value continuously maintains a small value, it means that the fixed position is set correctly.
Conversely, if this value continues to maintain a large value, there is a possibility that the fixed position being
set is offset from the true value.
If you know that the fixed position is set correctly, this value is an indicator of the reliability of the position
information calculated every second. For example, if this value is stable and maintains a small value, the
positioning calculation per second can be performed satisfactorily, and it can be inferred that the time
calculated by positioning calculation and 1PPS is also good. Conversely, if this value becomes larger or
smaller, it can be inferred that the reception environment is bad and the positioning calculation is disturbed
under the influence of multipath. At this time, 1PPS stability is expected to deteriorate.
Furthermore, this value can also be used for detection of anomaly of the antenna and spoofing signal. When
this value suddenly jumped from a small value to a large value in spite of knowing that the fixed position was
set correctly, it is expected to be caused by a sudden deterioration of the reception environment or a reception
of a spoofing signal by a malicious person. In this case, since the time and 1PPS calculated from positioning
calculation may be greatly jumped, risk avoidance is recommended in consideration of them.
31
GT-88
Protocol Specifications
SE18-600-003-00
[*2] Receiver status
The operation status of this product is displayed in BIT unit. The meaning of each BIT is as follows. If two or
more BIT conditions are satisfied at the same time, they are displayed as a logical sum of these BITs.
BIT (LSB=0)
Item
00 to 03
Antenna current
detection
04 to 07
Spoofing signal
detection
08 to 11
Operation status of
NLOSMASK mode
12 to 15
Energization time
16 to 19
20 to 23
24 to 27
Reserved
Reserved
Reserved
28 - 31
Antenna installation
environment
Description
0: Normal
1: Antenna short
2: Antenna open
3: No antenna voltage
Notify when a spoofing signal is detected. [*3]
0: Spoofing signal is not detected.
1: Spoofing signal is being detected.
Notify the processing status of multipath countermeasure set with
the NLOSMASK command.
0: NLOSMASK mode OFF
1: Step 1 in NLOSMASK mode
2: Step 2 in NLOSMASK mode
3: Step 3 in NLOSMASK mode
Total energization time since turning on the power supply of this
product
0: Less than 1 hour
1: 1 hour elapsed
2: 1 day elapsed
3: 7 days elapsed
4: 30 days elapsed
Determination result of the installation environment of the antenna
connected to this product [*4]
0: No position fix or non-positioning environment
1: Open sky environment
2: Semi-shielding environment
3: High shielding environment
[*3]
When an apparent abnormality (excluding the unhealth satellite) is seen in the contents of the navigation
message received from one of the GNSS satellites after the initial positioning using the appropriate GNSS
satellite, while the message is being received, 1 is set for the bit of this field. Error messages found by this
detection are discarded. Also, the satellite that broadcasts it will not be used for positioning.
[*4]
It is one of the indicators to judge whether the antenna installation place is good or bad, it does not guarantee
the performance.
32
GT-88
Protocol Specifications
SE18-600-003-00
6.13 CRZ (TPS4) – GCLK Frequency and Control
Format:
$PERDCRZ , TPS4 , Freq mode , Freq status , GCLK accuracy ,
1
2
3
Cnt1 , Cnt2 ,
7
8
4
Drift
,
IDtag
9
10
Field
1
Data
TPS4
Range
-
Default
-
2
Freq mode
1 to 9
(1 byte)
1
3
Freq status
4
GCLK accuracy
5
E
6
De
0, 1
(1 byte)
0, 1
(1 byte)
0
0
-999999 to
+999999
(7 bytes)
-
-999999 to
+999999
(7 bytes)
-
0000000 to
999999
(7 bytes)
0000000 to
999999
(7 bytes)
-99999 to
+99999
(6 bytes)
E
,
5
,
6
, Reserve , Revision
11
De
*hh
12
Description
Command name
Frequency mode
1: WARMUP / 2: LOCK
3: FREERUN / 4: FREERUN
5: PULLIN / 6: PULLIN
7: ECLK_LOCK / 8: ECLK_HOLDOVER
9: ECLK_FREERUN
0: GCLK frequency stop
1: GCLK frequency output
0: GCLK frequency is being stabilized
1: GCLK PPS and frequency is stable
Phase difference between synchronization target
and GCLK PPS
The closer to 0, it means synchronizing with the
synchronization target.
Amount of change in phase difference between
synchronization target and GCLK PPS
It is the difference between the phase difference
one second before and the current one.
-
Normal mode: Duration of LOCK mode
ECLK mode: HOLDOVER possible remaining time
-
Normal mode: Duration other than LOCK mode
ECLK mode: Learning time of frequency
-
Clock drift for built-in 26 MHz TCXO is displayed
with 10 times value of ppb. [*1]
7
Cnt1
8
Cnt2
9
Drift
10
IDtag
(6 bytes)
-
11
Reserve
-
12
Revision
(4 bytes)
0x00 to 0xFF
(4 bytes)
Product name and last two digits of version
In case of GT-88 of “4850557009”
Then 8800 + 09 = 880009
Reserve field
-
Software revision
Example:
$PERDCRZ,TPS4,2,0,1,+000000,+000000,+000801,+000000,-09029,880009,0x10,0x63*03
Frequency mode: LOCK / GCLK frequency: Not output / GCLK PPS and GCLK frequency: stable
Phase difference: 0 / Duration of LOCK mode: 801 seconds / Duration other than LOCK mode: 0
Clock drift: +902.9 [ppb] / IDtag: GT-88 version 09 / Software revision: 0x63
33
GT-88
Protocol Specifications
SE18-600-003-00
[*1] Clock drift
The Drift field of TPS 4 shows frequency shift amount with respect to TCXO with nominal frequency of 26 MHz
built in this product by ten times value of ppb. This is obtained by positioning calculation of GNSS and is
generally called clock drift. There are two causes of clock drift fluctuation: TCXO origin (TCXO aging and
temperature variation characteristics etc.) and GNSS origin (positioning calculation error using GNSS signal).
Since this product adjusts 1PPS to the synchronization target based on this clock drift, this value and 1PPS
output value correlate. By observing this value, it is possible to estimate fluctuation of 1PPS.
For example, when there is no temperature fluctuation around this product, clock deviation caused by TCXO is
not so large. Therefore, in an environment like an open sky, the clock drift maintains a relatively stable value.
Meanwhile, in the case of an adverse condition where the buildings are lined up, short-term clock drift tends to
be disturbed due to the GNSS caused by multipath signals and others.
In case of GNSS interruption, since the clock drift cannot be calculated by the positioning calculation, the last
value is maintained. However, when a GNSS interruption occurs in ECLK mode and the mode transitions to
HOLDOVER, clock drift is calculated continuously based on the frequency input to the ECLK pin.
34
GT-88
Protocol Specifications
SE18-600-003-00
6.14 CRG – QZSS L1S Disaster and Crisis Management Report Message
The DC report message broadcasted with QZSS L1S signal is output. [*1]
In order to receive messages in this sentence, it is necessary not only to output this sentence but also to be set
to receive the QZSS L1S signal with the GNSS command.
Format:
$PERDCRG , DCR ,
1
Field
1
2
Data
DCR
sequence
3
prn
4
type
5
dcreport
sequence
,
2
Range
1 to 4
Null,
83 to 91
Null,
43, 44, 63
XX・・・・・・・・X
|
|
MSB
LSB
prn
3
,
type
, dcreport
4
*hh
5
Description
QZSS L1S DC Report
Sequence number of sentence
PRN number of satellite broadcasted the message
Message type [*2]
Message is output when decoding is successful.
It outputs 212 BITS (53 Bytes) which is the DATA FIELD part as
a hexadecimal number sequence (0 to F). [*2]
Example:
$PERDCRG,DCR,1,85,43,7C4E43C001611580000000000000000000000000000000000004A*29
$PERDCRG,DCR,2,84,43,7C4E43C001611580000000000000000000000000000000000004A*2B
$PERDCRG,DCR,3,,,*1F
$PERDCRG,DCR,4,,,*18
[*1]
This sentence outputs the information obtained by receiving the QZSS L1S signal as it is. The content of the
DC report message needs to be interpreted by the host based on the user interface specification of the Cabinet
Office. Please be aware that depending on the timing of message decoding, two different messages may be
output from the same satellite in one second. Also, even if receiving a DC report message, when the CRC of
the message does not match, Fields 3 to 5 of this sentence will be Null.
[*2]
When the prn is Null, this field is also Null.
35
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Protocol Specifications
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6.15 CRJ – Detection Status of Jamming Signal
This sentence outputs the status of Anti-Jamming function.
Format:
$PERDCRJ , FREQ ,
1
type
, LineMax ,
Line
2
3
4
, Jamming 1 Freq , Jamming 1 Signal Peak ,
5
Jamming 2 Freq
7
Field
1
Data
FREQ
Range
-
Default
-
2
Type
GP or GL
-
3
4
LineMax
Line
1 to 4
1 to 4
NULL
NULL
5
Jamming 1 Freq
NULL or
10 bytes
NULL
6
Jamming 1
Signal Peak
1 ~ 255
NULL
7
Jamming 2 Freq
NULL or
10 bytes
NULL
8
Jamming 2
Signal Peak
1 ~ 255
NULL
6
, Jamming 2 Signal Peak
*hh
8
Description
Command name
Frequency band of this sentence
GP: GPS
GL: GLONASS
Total number of output lines for each band information
Current output line for each band information
First frequency of the jamming signal masked by the
Anti-Jamming function is indicated by 4 digits of
integer part and 5 digit of decimal part.
Signal strength of the first frequency of the jamming
signal masked by the Anti-Jamming function
The larger the value, the stronger the jamming signal.
Second frequency of the jamming signal masked by
the Anti-Jamming function is indicated by 4 digits of
integer part and 5 digit of decimal part.
Signal strength of the second frequency of the
jamming signal masked by the Anti-Jamming function
The larger the value, the stronger the jamming signal.
Example:
$PERDCRJ,FREQ,GP,,,,,,*4F
$PERDCRJ,FREQ,GL,1,1,1601.999787,171,,*4D
Jamming signal in GPS band is not detected.
In GLONASS band, frequency of 1601.999787 MHz is detected at signal strength 171 and masked by the
Anti-Jamming function.
[Precautions for use]
Anti-Jamming function works up to 8 channels only for GPS and GLONASS.
Up to 5 sentences may be output depending on the number of jamming signals being detected.
When detecting more than nine jamming signals, this function masks in order from the stronger signal.
36
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Protocol Specifications
SE18-600-003-00
6.16 CRP – High Resolution Current Position
This sentence displays position information with higher resolution than GNS or GGA sentence.
Format:
$PERDCRP ,
LatDegree
,
LonDegree
1
,
2
Field
Data
Range
1
LatDegree
-90.0000000 to
90.0000000
2
LonDegree
-180.0000000 to
180.0000000
3
Altitude
-1000.00 to
18000.00
Altitude
*hh
3
Description
Current position (Latitude) [degree] [*1]
A positive number means the north latitude and a negative
number means the south latitude.
Current position (Longitude) [degree] [*1]
A positive number means the east longitude and a negative
number means the west longitude.
Current altitude [meter] [*1]
Example:
$PERDCRP,+34.1234567,-51.6543210,35.12*47
34.1234567 deg N 51.6543210 deg W
Altitude: 35.12 m
[*1]
The fixed position is displayed in TO mode.
37
GT-88
Protocol Specifications
SE18-600-003-00
6.17 CRQ – SAR / RLM Information Broadcasted by Galileo Satellites
This sentence outputs the Search and Rescue (SAR) and the Return Link Message (RLM) received from
Galileo satellites.
Format:
$PERDCRQ , SentNum , SentIndex , Prn_1 , Sar_1 [, Prn_2 , Sar_2 ,
1
2
3
4
5
6
Prn_3 , Sar_3 , Prn_4 , Sar_4 ]
7
Field
1
2
Data
SentNum
SentIndex
Range
1 to 2
1 to 2
3
Prn_1
01 to 36
or NULL
4
Sar_1
000000 to 3FFFFF
or NULL
5
Prn_2
01 to 36
or NULL
6
Sar_2
000000 to 3FFFFF
or NULL
7
Prn_3
01 to 36
or NULL
8
Sar_3
000000 to 3FFFFF
or NULL
9
Prn_4
01 to 36
or NULL
10
Sar_4
000000 to 3FFFFF
or NULL
8
9
*hh
10
Description
Total number of CRQ sentence in this second
Number for identifying the number of lines in this sentence
Galileo satellite number that decoded the message
(This field is NULL when it is impossible to decode the
SAR/RLM)
SAR/RLM message [*1]
(This field is NULL when it is impossible to decode the
SAR/RLM)
Galileo satellite number that decoded the message
(This field is NULL when it is impossible to decode the
SAR/RLM)
SAR/RLM message [*1]
(This field is NULL when it is impossible to decode the
SAR/RLM)
Galileo satellite number that decoded the message
(This field is NULL when it is impossible to decode the
SAR/RLM)
SAR/RLM message [*1]
(This field is NULL when it is impossible to decode the
SAR/RLM)
Galileo satellite number that decoded the message
(This field is NULL when it is impossible to decode the
SAR/RLM)
SAR/RLM message [*1]
(This field is NULL when it is impossible to decode the
SAR/RLM)
Example:
$PERDCRQ,2,1,01,2AAAAA,02,2AAAAA,10,100000,11,200000*41
$PERDCRQ,2,2,13,2AAAAA,35,2AAAAA,,,,*47
SAR/RLM are received from Galileo satellite 01, 02, 10, 11, 13, 35.
$PERDCRQ,1,1,,*43
The receiver cannot decode the data or is not set to receive Galileo.
[*1]
It is data contained in I/Nav odd page that is decoded from Galileo E1-B signal. MSB is far leftmost bit.
38
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Protocol Specifications
SE18-600-003-00
6.18 ACK – Output the Command Reception Check
This sentence is output when this product receives the checksum of the command.
Format:
$PERDACK , Command , Sequence , Sub-command
1
2
*hh
3
Field
1
Data
Command
Range
-
Default
-
2
Sequence
-1 to 255
0
3
Sub-command
-
-
Description
First field of received command
The number of times successful for the reception.
It is added 1 whenever it succeeds in command
reception, and 0 to 255 is repeated. When command
reception is failed, -1 is returned.
The positive number means ACK, and the negative
number means NACK.
Second field of received command
Example:
$PERDACK,PERDAPI,-1,PPS*72
PERDAPI,PPS command input is failed.
6.19 MSG – Event Driven Message
This sentence is output when certain events occur. This is a sentence for FURUNO engineer use only.
Format:
$PERDMSG , key
1
Field
1
2
Data
key
string
[,
string ]
*hh
2
Range
-
Default
-
Description
Alphanumeric event indicator
Description of event
Example:
$PERDMSG,1A*06
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GT-88
Protocol Specifications
SE18-600-003-00
6.20 VERSION – Software Version
Format:
$PERDSYS , VERSION ,
Device
, Version ,
Reason
2
3
4
1
Field
1
2
3
Data
VERSION
Device
Version
Range
-
Default
-
4
Reason
BOOT,
QUERY,
UART1
-
5
Reserve
-
, Reserve
*hh
5
Description
Command name
Device name
Version number
Output condition
BOOT: Startup
QUERY: Response to VERSION command
UART1: Response to UART1 command
Reserve field
Example:
$PERDSYS,VERSION,OPUS7_SFLASH_MP_64P,ENP708A1830501T,QUERY,GT88*07
6.21 GPIO – General Purpose Input / Output
Format:
$PERDSYS ,
GPIO
1
,
State
*hh
2
Field
1
Data
GPIO
Range
-
Default
-
2
State
H or L
-
Description
Command name
GPIO state [*1]
H: High
L: Low
Example:
$PERDSYS,GPIO,HHHHLLLLL*07
[*1]
The most significant digit represents GPIO 0 and the least significant digit represents GPIO 8.
40
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Protocol Specifications
SE18-600-003-00
6.22 FIXSESSION – Fix Session
This is a sentence for FURUNO engineer use only. It is automatically output at startup, restart, and initial
positioning.
Format:
$PERDSYS , FIXSESSION , Reserve1 , Reserve2 , Reserve3 *hh
1
Field
1
2
3
4
2
Data
FIXSESSION
Reserve1
Reserve2
Reserve3
Range
-
3
Default
-
4
Description
Command name
Reserve field
Reserve field
Reserve field
6.23 ANTSEL – Antenna Selecting
This sentence is output when the following events occur:
- Initialization at power on
- Reception of $PERDSYS,ANTSEL,QUERY command
- $PERDSYS,ANTSEL command input
Format:
$PERDSYS , ANTSEL ,
1
Field
1
Input
2
Data
ANTSEL
Range
-
2
Input
FORCE1H,
FORCE1L,
FORCE2,
FORCEFS
3
LNA mode
1AUTO,
1HIGH,
1LOW
,
LNA mode
*hh
3
Description
Command name
GNSS antenna input setting
FORCE1H: LNA High gain mode
FORCE1L: LNA Low gain mode
FORCE2: Reserved
FLEXFS: LNA switching by hardware
LNA mode
1AUTO: Set by hardware
1HIGH: High gain mode
1LOW: Low gain mode
41
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Protocol Specifications
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7 Input Commands
These are input commands for the protocol of the receiver.
7.1
API [GNSS] – Satellite System Configuration
COLD restart (time also cleared) is run when satellite system configuration is changed from or to GLONASS
only fix configuration. In the others configurations HOT restart is run.
To turn off the use of GPS satellites, please also set the TIMEALIGN command properly.
Format:
$PERDAPI , GNSS , TalkerID , Gps , Glonass , Galileo , Qzss , Sbas/L1s *hh
1
Field
1
Data
GNSS
2
TalkerID
3
2
3
4
Range
AUTO
LEGACYGP
GN
Default
-
Gps
0, 2
2
4
Glonass
0, 2
2
5
Galileo
0, 2
0
6
Qzss
0, 2
2
7
Sbas/L1s
[*1]
0 to 4
1
GN
Example:
$PERDAPI,GNSS,AUTO,2,2,0,2,2*41
Use: GPS, GLONASS, QZSS(L1C/A), SBAS
Not receive: QZSS(L1S)
5
7
6
Description
Command name
Talker ID
See Section 5.3 for details.
GPS setting
0: Do not receive
2: Receive
GLONASS setting
0: Do not receive
2: Receive
Galileo setting
0: Do not receive
2: Receive
QZSS (L1C/A) setting
0: Do not receive
2: Receive
SBAS / QZSS L1S
0: Do not receive either
1: Differential fix with SBAS
2: In addition to the above 1, SBAS is used in
positioning calculation
3: Receive QZSS L1S (No SLAS correction)
4: Receive QZSS L1S (SLAS correction)
Mask: Galileo
[*1]
SBAS and QZSS L1S cannot be received at the same time. Only one of them can be used.
The current setting value can be checked by the following command.
$PERDAPI,GNSS,QUERY*18
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Protocol Specifications
SE18-600-003-00
7.2
API [PPS] – PPS Setting
Various setting status of PPS can be confirmed by TPS2 sentence.
Format:
$PERDAPI , PPS , Type , Mode , Period , Pulse width , Cable delay ,
1
2
3
4
5
6
Polarity [, PPS acc threshold ]
7
Field
1
Data
PPS
2
Type
Range
LEGACY,
GCLK
Default
LEGACY
3
Mode
0 to 4
3
4
Period
0, 1
0
5
Pulse width
200
6
Cable delay
1 to 500
-100000 to
100000
7
Polarity
0, 1
0
8
PPS acc
threshold
5 to 9999
0
1000
*hh
8
Description
Command name
PPS type [*1]
PPS output mode
0: Always stop
1: Always output
2: Output when the time is fixed after GNSS position fix
3: In addition to the above 2, output when there is no
TRAIM error
4: Output only when estimated accuracy is less than
threshold
PPS output interval
0: 1PPS
1: PP2S
PPS pulse width [msec]
PPS cable delay [nsec]
PPS is delayed by setting a positive value.
PPS polarity
0: Rising edge
1: Falling edge
Falling edge can be selected only with GCLK PPS and 1
PPS.
Threshold of estimated accuracy [nsec]
This threshold is used for mode 4. This field is
ommisible.
Example:
$PERDAPI,PPS,LEGACY,1,0,200,0,0,25*29
PPS type: LEGACY / PPS output mode: Always output / PPS output interval: 1PPS
PPS pulse width: 200 msec / Cable delay: 0 nsec / PPS polarity: Rising edge
PPS acc threshold: 25 nsec
[*1]
When GCLK PPS is set, control of GCLK frequency is restarted from WARMUP again.
43
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Protocol Specifications
SE18-600-003-00
7.3
API [FREQ] – GCLK Frequency Setting
When inputting this command, control of GCLK frequency is restarted from WARMUP again.
Format:
$PERDAPI , FREQ ,
1
Mode
, Freq
2
[,
Duty
3
,
Offset ]
4
Field
1
Data
FREQ
Range
-
Default
-
2
Mode
0, 1
0
3
Freq
10 to
40000000
10000000
(10MHz)
4
Duty
10 to 90
50
5
Offset
0 to 99
0
*hh
5
Description
Command name
GCLK output mode
0: Do not output
1: Output
GCLK frequency [Hz]
Duty cycle [%] [*1]
It is omissible after the 4th field.
Phase delay of frequency from GCLK PPS [%]
When set to 50%, the phase is inverted with respect to
the default.
Example:
$PERDAPI,FREQ,1,10000000*47
GCLK output mode: Output GCLK output frequency: 10MHz
[*1]
The duty cycle (Thigh / Tcycle) is below.
The current setting value can be checked by the following command.
$PERDAPI,FREQ,QUERY*11
[Notes on GCLK]
Stability of GCLK PPS and GCLK frequency depends on the frequency value set with this command. For
details, please refer to the hardware specifications.
44
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Protocol Specifications
SE18-600-003-00
7.4
API [SURVEY] – Position Mode Setting
HOT restart is occurred when the position mode is shifted to the NAV mode.
Format:
$PERDAPI , SURVEY , Position mode [, Sigma threshold , Time threshold [,
1
2
3
4
Latitude , Longitude , Altitude ]] *hh
5
Field
1
Data
SURVEY
Range
-
Default
-
2
Position
mode
0 to 3
1
3
Sigma
threshold
0 to 255
0
4
Time
threshold
0 to 10080
1440
(24 hours)
5
Latitude
-90.0000000
to
90.0000000
0
6
Longitude
-180.0000000
to
180.0000000
0
7
Altitude
-1000.00 to
18000.00
0
6
7
Description
Command name
Position mode [*1]
0: NAV mode
1: SS mode
2: CSS mode
3: TO mode
Sigma threshold which changes automatically to TO
mode. [m]
When the threshold value is 0, it is not used. [*2]
Time threshold which changes automatically to TO
mode. [minute]
When the threshold value is 0, it is not used. [*2]
Latitude for hold position in TO mode. [degree] [*3]
A positive number means the north latitude and a
negative number means the south latitude.
This field can be set only when position mode is 3.
It accepts up to the seventh decimal place.
Longitude for hold position in TO mode. [degree] [*3]
A positive number means the east longitude and a
negative number means the west longitude.
This field can be set only when position mode is 3.
It accepts up to the seventh decimal place.
Altitude above sea level for hold position in TO mode.
[m] [*3]
This field can be set only when position mode is 3.
It accepts up to two decimal place.
Example:
$PERDAPI,SURVEY,1,10,1440*74
Mode: SS mode
When the variance value of the estimated position is 10 or less and the number of calculation times of the
estimated position reaches 86400 times, it automatically transits to TO mode.
$PERDAPI,SURVEY,3,0,0,37.7870,-122.4510,31*48
Mode: TO mode Sigma threshold: 0 Time threshold: 0
Fixed position: 37.7870 degrees north 122.4510 degrees west
Altitude: 31 m
[*1]
Whether the calculation result of the estimated position is discarded when changing the position mode is as
follows.
45
B
GT-88
Protocol Specifications
SE18-600-003-00
NAV
F
H
G
F
H
E
SS
I
F
TO
A,C
I
H
G,J
I
J
G,
CSS
D
Transition condition
A
B
C
D
E
F
G
H
I
J
After first power on, or after factory restart (default)
After power on in case that last mode is NAV mode.
After power on in case that last mode is SS mode.
After power on in case that last mode is CSS mode.
After power on in case that last mode is TO mode.
Set to NAV mode
Set to TO mode
(After initial positioning, or when fixed position input)
Set to SS mode
Set to CSS mode
The condition of survey is satisfied.
Note: This product starts in TO mode when the position
mode changes to TO mode by satisfying the transition
condition before power off.
Survey position and number
of times of survey process
Discard
Discard
Discard
Keep
Keep
Discard
Keep
Discard
Discard
Keep
[*2]
When both Sigma threhold and Time threshold are satisfied, the position mode transits to TO mode. If you
want to use only one of the thresholds, set the threshold value of the one not used to 0.
[*3]
In some cases, the actual input position and the position indicated by the sentence may rarely differ slightly on
the scale of the least significant digit. However, it is due to the conversion error of the coordinate system at
sentence display, there is no problem in performance. Due to the convenience of trigonometric calculations,
when the position near the North Pole and South Pole points is set, there may be some error included in the
reflected position.
[Note]
Under the open sky environment, by using the default setting, it automatically transitions to TO mode after
calculating the fixed position with high precision.
On the other hand, if you want to automatically transition to TO mode after computing a precise fixed position
in an environment that is not an open sky such as an urban area, we recommend setting the Sigma threshold
in the range of about 5 to 50 in addition to the Time threshold. As the threshold value to be set decreases, it
may take time to automatically transition to the TO mode. However, since it transits to TO mode after acquiring
a more definite fixed position, the time (1PPS) performance obtained after that is good.
46
GT-88
Protocol Specifications
SE18-600-003-00
7.5
API [RESTART] – Restart Command
The details of RESTART command are described below. This command does not delete the backup data in
FLASH.
Format:
$PERDAPI , RESTART [ , Restart type ]
1
Field
1
2
*hh
2
Data
RESTART
Range
-
Default
-
Restart type
HOT
WARM
COLD
FACTORY
-
Description
Command name
Restart mode
The backup data retained after restart varies depending
on the restart mode.
See Chapter 8 for details.
When this field is omitted, the restart mode is HOT.
Example:
$PERDAPI,RESTART,COLD*08
Mode: COLD restart
47
GT-88
Protocol Specifications
SE18-600-003-00
7.6
API [FLASHBACKUP] – Back up to FLASH ROM
Format:
$PERDAPI , FLASHBACKUP , Type
1
Field
1
Data
FLASHBACKUP
*hh
2
Range
-
Default
-
Description
Command name
Select the item to be stored in FLASH.
Each bit corresponds to each command setting value.
Please set by OR. When this command is entered
more than once, only the command of the bit specified
by this command is stored at the end.
2
Type
0x0000 to
0xFFFF
0x0000
0x00: Clear the data stored in FLASH
0x01: Back up FREQ command
0x02: Back up DEFLS command
0x04: Back up TIMEALIGN command
0x08: Reserved
0x10: Back up FIXMASK command
0x20: Back up GNSS command
0x40: Back up PPS command
0x80: Back up ECLK command
0x100: Back up NLOSMASK command
0x200: Back up SURVEY command [*1]
Reserved after 0x400
Example:
$PERDAPI,FLASHBACKUP,0x03*4E
Back up FREQ and DEFLS command setting.
[*1]
The SURVEY command can not be backed up to FLASH in CSS mode and TO mode. Please use it in NAV
mode or for threshold setting in SS mode.
[Precautions for use]
The contents stored by this command are deleted by software update.
The contents stored by this command are not deleted by RESTART command (including FACTORY).
When this command is input, positioning is temporarily interrupted and HOT restart is performed
thereafter.
Do not turn off the power for at least 4 seconds after this command input.
The current setting value can be checked by the following command.
$PERDAPI,FLASHBACKUP,QUERY*4F
The response of QUERY is displayed in a command list format over multiple lines. An output example of
backing up FREQ, DEFLS and TIMEALIGN is as follows.
$PERDCFG,FORMAT,ESIP*4D
$PERDAPI,FREQ,0,10000000,50,0*73
$PERDAPI,DEFLS,18*0A
$PERDAPI,TIMEALIGN,4*37
$PERDACK,PERDAPI,5,FLASHBACKUP*56
48
GT-88
Protocol Specifications
SE18-600-003-00
7.7
API [DEFLS] – Default Leap Second Setting
COLD restart (time also cleared) is run when this command is input.
Format:
$PERDAPI , DEFLS , Sec
1
Field
1
2
Data
DEFLS
Sec
*hh
2
Range
-99 to 99
Default
18
Description
Command name
Default leap second
Example:
$PERDAPI,DEFLS,19*0B
Default leap second: 19 second
The current setting value can be checked by the following command.
$PERDAPI,DEFLS,QUERY*49
49
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Protocol Specifications
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7.8
API [TIMEZONE] – Local Zone Time Setting
The current setting value can be checked in ZDA sentence. (Except sec field)
Format:
$PERDAPI , TIMEZONE ,
1
Sign
, Hour ,
Minute
2
3
4
Field
1
Data
TIMEZONE
Range
-
Default
-
2
Sign
0 to 1
0
3
Hour
0 to 23
0
4
Minute
0 to 59
0
5
Sec
E, M
E
[, Sec]
*hh
Description
Command name
LZT sign
0: Positive
1: Negative
This setting is applied only to the ZDA sentence.
LZT (Hour)
This setting is applied only to the ZDA sentence.
LZT (Minute)
This setting is applied only to the ZDA sentence.
By using this field, user can change the relationship
between 1PPS and time stamp of sentence. This
setting is applied to all sentences which time is
output. Please use this field by default as it is
unnecessary.
E: Time is output with the relationship of [* 1] below.
Time stamp shows the time of next 1PPS output.
This output mode is eSIP specification.
M: Time is output with the relationship of [* 2] below.
Time stamp shows the time of last 1PPS output.
This output mode is M12 specification.
Example:
$PERDAPI,TIMEZONE,0,9,0*69
LZT: +9 hours
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[*1]
Time = t
Time = t + 1
Time = t + 2
Reference Time
1PPS
Serial data
Time = t + 1
Time = t + 2
25 - 75 ms
25 - 75 ms
25 - 75 ms
[*2]
Time = t
Time = t + 1
Time = t + 2
Reference Time
1PPS
Serial data
Time = t
Time = t + 1
25 - 75 ms
25 - 75 ms
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7.9
API [TIMEALIGN] – Time and PPS Alignment Setting
Please send this command only before initial positioning of COLD start.
Format:
$PERDAPI , TIMEALIGN , Mode *hh
1
Field
1
2
Data
TIMEALIGN
Mode
2
Range
1 to 6
Default
2
Description
Command name
Select the output time and PPS synchronization target [*1]
Example:
$PERDAPI,TIMEALIGN,2*31
Apply the leap second to the output time, PPS synchronizes with UTC time.
The output time means the time field of GNS, ZDA and TPS1 sentences.
[*1]
The details of each time alignment mode are as follows:
Mode
Output time
PPS synchronization
target
1
Leap second is
ignored
GPS time
2
UTC (USNO) time
3
UTC (SU) time
4
Leap second is
applied
UTC (EU) time
5
UTC (NICT) time
6
GPS time
Description
Ignore leap second and UTC parameter, output GPS
time, and synchronize PPS with GPS time.
Output time that leap second is applied.
1PPS is synchronized with UTC (USNO) time.
[*] Reception of GPS satellite is required.
Output time that leap second is applied.
1PPS is synchronized with UTC (SU) time.
[*] Reception of GLONASS satellite is required.
Output time that leap second is applied.
1PPS is synchronized with UTC (EU) time.
[*] Reception of Galileo satellite is required.
Output time that leap second is applied.
1PPS is synchronized with UTC (NICT) time.
[*] Reception of QZSS satellite is required.
Output time that leap second is applied.
Ignore UTC parameter, and synchronize PPS with
GPS time.
The current setting value can be checked by the following command.
$PERDAPI,TIMEALIGN,QUERY*49
[Restrictions]
This command selects which satellite to acquire UTC parameters (leap seconds, leap second insertion
timing, UTC correction coefficient, etc.). If not set properly, leap seconds update or leap second
insertion may not be performed. Therefore, please set this command appropriately according to the
setting with the GNSS command. In the default state, UTC parameters are acquired from the GPS
satellites. When turning off the use of GPS satellites with the GNSS command, please select another
satellite for UTC parameter acquisition again from the satellites set for use with the GNSS command.
GLONASS broadcasts the time including the leap second and does not broadcast the cumulative value of the
leap second. When Mode=1 is selected during GLONASS standalone positioning, in order to match the correct
output time, it is necessary to set the correct default leap second with the DEFLS command beforehand.
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7.10 API [TIME] – Time Setting
This command can be used before initial positioning only when all of the following conditions are satisfied.
After October 11, 2037 that is the timing of internal rollover
Not use GLONSS or Galileo
Start up with no time backup
By setting the appropriate current date with this command, it is possible to output the correct date even after
internal rollover. For details of internal rollover, please also refer to the technical document (SE18-100-034).
Format:
$PERDAPI , TIME , Time of date , Day , Month , Year
1
Field
1
Data
TIME
2
Time of
date
3
4
5
Day
Month
Year
2
Range
00 to 23
00 to 59
00 to 59
1 to 31
1 to 12
2018 to 2099
3
4
Default
8
1999
*hh
5
Description
Command name
Set the current hour, minute, second with 2 digits each.
It does not need to be accurate.
Current day
Current month
Current year
Example:
$PERDAPI,TIME,021322,24,11,2020*64
Time: 02:13:22 on 24th November, 2020
[Restrictions]
This command is required to input correct date within +/- 512 weeks.
Do not use this command after position fix since the time obtained from satellites is used.
For the output time, please also refer to corresponding items in Chapter 2.
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7.11 API [FIXMASK] – Positioning and Satellite Mask Setting
Format:
$PERDAPI , FIXMASK , Mode , Elevmask , Reserve , SNRmask ,
1
2
3
4
5
IDSM
6
Prohibit SVs
Prohibit SVs
Prohibit SVs
Prohibit SVs
Prohibit SVs
,
,
,
,
(GPS)
(GLONASS)
(Galileo)
(QZSS)
(SBAS)
7
8
9
10
11
Field
1
2
Data
FIXMASK
Mode
Range
USER
Default
-
3
Elevmask
0 to 90
0
4
Reserve
0
0
5
SNRmask
0 to 99
0
6
IDSM
Prohibit SVs
(GPS)
Prohibit SVs
(GLONASS)
Prohibit SVs
(Galileo)
Prohibit SVs
(QZSS)
0
32BIT
(HEX)
24BIT
(HEX)
36BIT
(HEX)
5BIT
(HEX)
0
Prohibit SVs
(SBAS)
19BIT
(HEX)
7
8
9
10
11
0
0
0
0
0
[,
] *hh
Description
Command name
Fixed value
Elevation mask [degree]
Only satellites at elevation above this value are used in
positioning.
Reserve field
Signal level mask [dB-Hz]
Only satellites with signal levels above this value are used
in positioning.
0 stable
GPS satellite number mask [*1]
Lowest order bit means SV=01.
GLONASS satellite number mask [*1]
Lowest order bit means SV=65.
Galileo satellite number mask [*1]
Lowest order bit means SV=01.
QZSS L1C/A Satellite number mask [*1]
In order from the lowest BIT, 93, 94, 95, 96, 99
SBAS Satellite number mask [*1]
Lowest order bit means SV=33. Set to 0 when using QZSS
L1S signal.
Example:
$PERDAPI,FIXMASK,USER,10,0,37,0,0x00000092,0x000001,0x000000000,0x00,0x20000*60
Elevation mask: 10 degrees Signal level mask: 37 dB-Hz
GPS mask: GPS (BIT2 = SVID 2), GPS (BIT5 = SVID 5) and GPS (BIT8 = SVID 8)
GLONASS mask: GLONASS (BIT1 = SVID 65)
SBAS mask: SBAS (BIT18 = SVID 50)
[*1]
Each BIT corresponds to one satellite. When entering, please add 0x to the beginning. Do not set the
command with a length exceeding the range.
The current setting value can be checked by the following command.
$PERDAPI,FIXMASK,QUERY*52
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7.12 API [OCP] – Detailed Elevation and Azimuth Mask Setting
The elevation mask can be set for each azimuth angle of 1 degree instead of the conventional unique elevation
angle mask. It is useful when fixedly installing in an environment where there are many shields such as urban
areas.
When this command is used with the elevation mask of FIXMASK command, the higher mask value is applied.
For example, if the elevation mask is set to 5 degrees with the FIXMASK command and the elevation mask of
30 degrees is set for the azimuth angle of 100 degrees with this command, the elevation mask 30 degrees is
applied only at the azimuth angle of 100 degrees, and at the other azimuth angles the elevation mask 5
degrees is applied.
Format:
$PERDAPI , OCP , az_1 , el_1 [, az_2 , el_2 [, … [, az_9 , el_9 ] … ] *hh
1
Field
1
2
3
…
18
19
Data
OCP
az_1
el_1
…
az_9
el_9
2
Range
000 to 359
00 to 99
…
000 to 359
00 to 99
3
4
Default
0
0
…
0
0
5
18
19
Description
Command name
Specify azimuth angle
Set elevation angle for the azimuth angle specified above
…
Specify azimuth angle
Set elevation angle for the azimuth angle specified above
Example:
$PERDAPI,OCP,015,45*1E
Set elevation mask 45 degrees for azimuth angle 15 degrees.
For all other azimuths, keep the state just before the command input.
$PERDAPI,OCP,015,5,244,21*1B
Set elevation mask 5 degrees for azimuth angle 15 degrees and elevation mask 244 degrees for azimuth
angle 21 degrees.
For all other azimuths, keep the state just before the command input.
[Note]
It is omissible after the 4th field. You can add 0 to the beginning or omit it. For example, if you input 015 or 15,
it accepts the same as 15.
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The following command can specify an azimuth range and set an elevation mask for that range. It is
convenient when you set the elevation mask manually.
Format:
$PERDAPI , OCP , RANGE , start_angle , end_angle ,
1
2
3
Field
1
2
Data
OCP
RANGE
Range
RANGE
Default
-
3
start_angle
0 to 359
0
4
end_angle
0 to 359
0
5
elevation
0 to 90
0
4
elevation
*hh
5
Description
Command name
Indicates that azimuth is specified as a range
Start position of the azimuth angle range
From this azimuth angle, specify the range in the clockwise
direction.
End position of the azimuth angle range
Determines the azimuth range with this azimuth as the end
point.
Set this elevation mask for the range specified above
Example:
$PERDAPI,OCP,RANGE,15,45,60*77
Set the elevation mask 60 degrees in the range from 15 to 45 degrees in the clockwise direction.
For all other azimuths, keep the state just before the command input.
$PERDAPI,OCP,RANGE,330,15,45*41
Set the elevation mask 45 degrees in the range from 315 to 15 degrees in the clockwise direction. (That is,
ranges from 315 to 359 degrees and from 0 to 15 degrees are specified.)
For all other azimuths, keep the state just before the command input.
[Note]
The current set value can be checked by one of the following commands. Since this sentence has a lot of
output, please choose according to the baud rate and the output of other sentences.
$PERDAPI,OCP,QUERY*4D
The setting value is output for all azimuth angles from 0 to 360 degrees. Since it is displayed in a total of 18
lines, the sentence output amount increases, and in some cases it may not be able to output all of them.
$PERDAPI,OCP,QUERY1*7C
The setting value is output for the first half azimuth angle from 0 to 180 degrees. It displays with a total of 9
lines.
$PERDAPI,OCP,QUERY2*7F
The setting value is output for the second half azimuth angle from 180 to 360 degrees. It displays with a total of
9 lines.
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The output format for QUERY is as follows.
Format:
$PERDAPI , OCP , num , el_0 , el_1 , … , el_19 *hh
1
2
3
4
Field
1
Data
OCP
Range
-
Default
-
2
num
01 to 18
-
3
4
…
23
el_0
el_1
…
el_19
00 to 99
00 to 99
…
00 to 99
0
0
…
0
23
Description
Command name
Current number of lines of OCP sentence.
In case of 01, the elevation mask value for the azimuth
angle 0 to 19 degrees is output, and in case of 02, the
elevation mask value for the azimuth angle 20 to 39
degrees is output on that line.
Elevation mask for azimuth angle “num * 20 + 0” degrees
Elevation mask for azimuth angle “num * 20 + 1” degrees
…
Elevation mask for azimuth angle “num * 20 + 19” degrees
Example:
$PERDAPI,OCP,01,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*06
$PERDAPI,OCP,02,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*05
$PERDAPI,OCP,03,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*04
$PERDAPI,OCP,04,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*03
$PERDAPI,OCP,05,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*02
$PERDAPI,OCP,06,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*01
$PERDAPI,OCP,07,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*00
$PERDAPI,OCP,08,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*0F
$PERDAPI,OCP,09,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*0E
$PERDAPI,OCP,10,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15,15*06
$PERDAPI,OCP,11,15,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*03
$PERDAPI,OCP,12,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*04
$PERDAPI,OCP,13,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*05
$PERDAPI,OCP,14,00,00,00,00,00,00,00,00,00,00,45,45,45,45,45,45,45,45,45,45*02
$PERDAPI,OCP,15,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45,45*03
$PERDAPI,OCP,16,45,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*01
$PERDAPI,OCP,17,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*01
$PERDAPI,OCP,18,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00*0E
Elevation mask 15 degrees in the range from 0 to 200 degrees and Elevation mask 45 degrees in the range
from 270 to 300 degrees are set.
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7.13 API [NLOSMASK] – NLOS Satellite Elimination Algorithm Setting
We recommend using the default setting when there is no particular need.
Format:
$PERDAPI , NLOSMASK ,
mode
1
, Threshold1 , Threshold2 , Threshold3
2
3
Field
1
Data
NLOSMASK
Range
-
Default
-
2
mode
0, 1
1
3
Threshold 1
0 to 3600
0
4
Threshold 2
0 to 99
30
4
*hh
5
Description
Command name
Algorithm to eliminate NLOS satellites [*1]
0：OFF / 1：ON
Time to intentionally hold the positioning calculation after
starting or restarting [second] [*2]
Signal level mask which is limitedly set only until the
probable position is calculated [dB-Hz] [*3]
After calculating the probable current position, this mask
setting will be invalid.
Threshold for determining which satellite is the NLOS
satellite [nsec] [*4]
5
Threshold 3
0 to 9999
50
The smaller the numerical value, the more severe the
condition of LOS satellite.
Example:
$PERDAPI,NLOSMASK,1,1000,40,50*4C
Use algorithm to eliminate NLOS satellites. Positioning is held for 1000 seconds after starting or restarting, and
then positioning calculation will start. Signal level mask 40 [dB-Hz] is applied until the probable position is
calculated, satellites below that are not used in positioning. After calculating the probable current position, the
signal level mask 40 is canceled, and only satellites within the threshold value of 50 ns are used in time
calculation.
The current setting value can be checked by the following command.
$PERDAPI,NLOSMASK,QUERY*1B
[*1]
Fine adjustment of this algorithm is possible by adjusting the threshold after the third field.
[*2]
Normally, general GNSS receivers tend to start positioning calculation as soon as possible when satellite
signals can be received. This is because they are tuned for solutions that require the need to quickly fix the
position for car navigation etc.
On the other hand, in the timing solution focused on long-term time stability, it is important to continually
determine the position and time rather than the initial positioning quickness.
The setting tuned for car navigation is effective for getting rough location information quickly. However,
depending on the positioning environment, there are concerns that positioning is performed with four satellites
including only NLOS satellites and the initial position is determined. This is because even if LOS satellites can
be found by searching enough time, positioning calculation is performed using the previously received
satellites. In this case, position accuracy is bad and time accuracy may be affected.
This field addresses such concerns. By setting a value in this field, deliberately delay the start of positioning
calculation and set a period to focus only on satellite search. GNSS satellites generally broadcast almanac
which is rough orbital information of the satellite in about 900 seconds cycle. By holding this time or more, it is
possible to drastically reduce the loss of the satellite existing above the sky.
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The counter to be compared with this threshold value is unconditionally incremented every second regardless
of the connection state of the antenna or reception environment after startup or restart. The counter is reset
only at restart.
This setting is not applied in the NAV mode.
[*3]
This field sets a signal level mask. The same setting can be done with the FIXMASK command. However,
unlike the setting of the FIXMASK command which is executed at all times, this setting is applied only for a
limited period until the probable position can be calculated.
In general, the signal level mask is considered useful for eliminating NLOS satellites. The setting of an
appropriate signal level mask is said to be useful for improving positioning accuracy. However, the persistent
signal level mask has a problem that it is difficult to use because there is a possibility that the satellite
interruption may be immediately caused when the reception environment deteriorates.
This field focuses on determining the fixed position which has a particularly large effect on the calculation of
time. The signal level is masked until the fixed position is roughly determined. After finding a certain position,
the mask is released. As a result, positioning can be continued while ensuring time accuracy even in a badly
conditioned environment with many shielding objects.
When using the signal level mask of the FIXMASK command together, the higher mask value is applied.
This setting is not applied in the NAV mode.
[*4]
This product is equipped with an algorithm that regards it as an NLOS satellite when the time until the satellite
signal arrives at the receiver is later than the expected time. This field can fine-tune the threshold to determine
it.
Even satellites that do not satisfy the threshold set in this field are counted as positioning satellites and also
displayed on the GSA sentence. Internally, the process of reducing the contribution to the positioning of the
target satellite is applied.
This setting may be applied even in the NAV mode.
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7.14 API [ECLK] – ECLK Mode Setting
Format:
$PERDAPI , ECLK ,
1
Mode [, ECLK freq , HO time ]
2
3
*hh
4
Field
1
Data
ECLK
Range
-
Default
-
2
Mode
0, 1
0
3
ECLK freq
1000000 to
40000000
(1 MHz to 40 MHz)
-
4
HO time
0 to 99999
-
Description
Command name
ECLK setting
0: Normal mode
1: ECLK mode
Nominal frequency of the oscillator input to the
ECLK pin
Not used in normal mode.
Holdover time when satellite interruption
Not used in normal mode.
Example:
$PERDAPI,ECLK,0,10000000,3600*6E
Normal mode / ECLK freq and HO time field are omitted.
$PERDAPI,ECLK,1,10000000,3600*6F
ECLK mode / Nominal frequency: 10 MHz / Holdover time: Up to 3600 seconds
The current setting value can be checked by the following command.
$PERDAPI,ECLK,QUERY*10
[ECLK mode]
ECLK mode maintains the performance of PPS and GCLK frequencies output by this product as much as
possible even while the satellite reception is interrupted by connecting an arbitrary oscillator frequency to the
ECLK pin of this product and acquiring the characteristic of the free running state of the oscillator frequency.
You can customize the holdover function by selecting the oscillator connected to the ECLK pin and setting the
holdover period.
Since it does not control the oscillator directly, it does not need to be a voltage controlled oscillator. An arbitrary
oscillator can be connected in a wide frequency range from 1 MHz to 40 MHz.
[Oscillator available for ECLK mode]
The oscillator that can be connected when using this mode must satisfy all of the following conditions.
Nominal frequency is within the range of 1 MHz to 40 MHz.
Output frequency does not stop or is not intermittent.
Output frequency does not change abruptly.
[Frequency mode in ECLK mode]
The following three modes are displayed in TPS4 sentence in ECLK mode.
ECLK_LOCK mode
ECLK_HOLDOVER mode
ECLK_FREERUN mode
For details, see the terms in Chapter 2.
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[Notes on ECLK mode]
The use of this mode may be limited to specific customers.
Although this mode seeks to stabilize the PPS and GCLK frequencies while the satellite reception is
interrupted by using the oscillator frequency connected to the ECLK pin, the performance is not
guaranteed numerically. In addition, its effect varies greatly depending on the performance of the
connected oscillator in its free running state. We strongly recommend that you evaluate the connected
oscillator and the actual output value of this product satisfactorily.
In this mode, only the LEGACY PPS type can be used. Cannot be used with GCLK PPS.
For ECLK_HOLDOVER mode, it is necessary to maintain ECLK_LOCK mode for 180 seconds or more
immediately before it. When the ECLK_LOCK mode period is less than 180 seconds and satellite
reception is interrupted or the frequency cannot be obtained from the ECLK pin, the mode transitions to
the ECLK_FREERUN mode.
HO time set with this command is the period for displaying ECLK_HOLDOVER mode with TPS4 sentence.
It is not a period for which this product guarantees the performance of PPS or GCLK frequency.
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7.15 API [ECLKCNT] – Measurement of ECLK pin frequency
Based on the GNSS time, measure and output the frequency input to the ECLK pin.
Format:
$PERDAPI , ECLKCNT ,
cnt
1
Field
1
2
Data
ECLKCNT
cnt
*hh
2
Range
-
0 to 100
Default
-
0
Description
Command name
Frequency average processing times
When set to 0, the output of this sentence stops. In the case
of 1 to 100, this sentence is output every second.
A value of 1 or more means moving average seconds when
outputting frequency. For example, when set to 10, the
sentence of every second will be output with high accuracy
with the moving average value in the last 10 seconds.
Example:
$PERDAPI,ECLKCNT,1*32
ECLKCNT sentence is output every second.
Response sentence is output every second as below.
$PERDAPI,ECLKCNT,9999995.43925,Hz*3F
$PERDAPI,ECLKCNT,9999995.42697,Hz*38
$PERDAPI,ECLKCNT,9999995.42089,Hz*31
$PERDAPI,ECLKCNT,9999995.41707,Hz*33
$PERDAPI,ECLKCNT,9999995.41626,Hz*31
$PERDAPI,ECLKCNT,9999995.41430,Hz*34
$PERDAPI,ECLKCNT,9999995.41275,Hz*33
$PERDAPI,ECLKCNT,9999995.41159,Hz*3E
$PERDAPI,ECLKCNT,9999995.41127,Hz*37
$PERDAPI,ECLKCNT,9999995.41035,Hz*35
$PERDAPI,ECLKCNT,9999995.40953,Hz*3D
[Notes]
Other than ECLK_LOCK mode, it is displayed at 0 Hz. The frequency control parameter is reset when this
command is input.
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7.16 API [CROUT] – CR Sentence Output Setting
Format:
$PERDAPI , CROUT , Type , Rate
1
2
*hh
3
Field
1
Data
CROUT
Range
-
Default
-
2
Type
G, J, P, Q,
W, X, Y, Z
W,X,Y,Z
3
Rate
W,X,Y,Z: 0 to 255
Others: 0 or 1
Description
Command name
Output CR sentence
Multiple sentences can be set at the same time.
Alphabets of outside range are reserved.
Output interval or stop setting
P,W,X,Y,Z:
1 to 255: Output interval [second]
0: Output stop
1
Others:
1: Output every event occurrence
0: Output stop
Reserved except for the above range
Example:
$PERDAPI,CROUT,W,1*4E
CRW (TPS1) sentence is output every second.
$PERDAPI,CROUT,XZ,3*19
CRX (TPS2) sentence and CRZ (TPS4) sentence are output every 3 seconds.
$PERDAPI,CROUT,W,0*4F
CRW (TPS1) sentence is stopped.
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7.17 CFG [NMEAOUT] – Standard NMEA Output Setting
Format:
$PERDCFG , NMEAOUT , Type , Interval
1
2
*hh
3
Field
1
Data
NMEAOUT
Range
-
Default
-
2
Type
[*1]
-
3
Interval
0 to 60
-
Description
Command name
Standard NMEA sentence
[*1] GGA, GLL, GNS, GSA, GSV, RMC, VTG, ZDA, ALL.
(ALL means all sentences from GGA to ZDA.)
Output interval [second]
When set to 0, output is stopped after outputting sentence
only once.
Example:
$PERDCFG,NMEAOUT,GGA,2*57
GGA sentence is output every 2 sec.
$PERDCFG,NMEAOUT,GSV,0*56
After outputting GSV sentence only once, stop outputting.
7.18 CFG [UART1] – Serial Communication Port Setting
Format:
$PERDCFG , UART1 , Baudrate *hh
1
2
Field
1
Data
UART1
Range
-
Default
-
2
Baudrate
4800, 9600, 19200,
38400, 57600, 115200,
230400, 460800
38400
Example:
$PERDCFG,UART1,115200*65
Baud rate: 115200 bps
64
Description
Command name
Baud rate [bps]
Depending on the hardware, it may not support
230400 bps or higher.
GT-88
Protocol Specifications
SE18-600-003-00
7.19 SYS [VERSION] – Software Version Request
This command requests output of software version information.
Format:
$PERDSYS , VERSION
*hh
1
Field
1
Data
VERSION
Range
-
Default
-
Description
Command name
Example:
$PERDSYS,VERSION*2C
7.20 SYS [GPIO] – GPIO Output Request
This command requests output of GPIO input / output information.
Format:
$PERDSYS ,
GPIO
*hh
1
Field
1
Data
GPIO
Range
-
Default
-
Description
Command name
Example:
$PERDSYS,GPIO*67
65
GT-88
Protocol Specifications
SE18-600-003-00
7.21 SYS [ANTSEL] – Antenna Input Setting
This command sets the LNA of the antenna, requests the output of the current state.
Format:
$PERDSYS , ANTSEL ,
Mode
1
Field
1
2
*hh
2
Data
ANTSEL
Range
-
Default
-
Mode
FORCE1H,
FORCE1L,
FORCE2,
FLEXFS,
QUERY
[*1]
Description
Command name
LNA mode
FORCE1H: Set LNA to High gain
FORCE1L: Set LNA to Low gain
FORCE2: Set LNA to FORCE2
FLEXFS: LNA is set by hardware
QUERY: Request ANTSEL sentence
Example:
$PERDSYS,ANTSEL,FORCE1H*7F
[*1]
It depends on the product as follows.
Product name
GT-88
ePV7010B
(eRideOPUS 7 chip 64pin with GT-88 software)
LNA mode
FLNA pin: LOW
FLNA pin: HIGH
FORCE1H
FORCE1L
FLEXFS
FORCE2
[Precautions for use]
Please set an appropriate LNA for the antenna. When it is not an appropriate LNA setting, this product may
cause reception failure of the satellite.
66
GT-88
Protocol Specifications
SE18-600-003-00
8 Backup of the Receiver Parameters (for BBRAM)
The GT-88 stores the satellite information, the positioning result and the command setting to a backup area,
and can use them at the next power on. The GT-88 has a BBRAM as a backup area. The BBRAM is a storage
area which can back up while the backup power supply (VBK) is available. The backup to the BBRAM
executes automatically every second. When inputting a command, the setting is backed up at the timing. The
stored data are erased by RESTART command and an interruption of the backup power supply.
The parameters which this receiver has backed up are shown below.
Table 8.1 Backup of Receiver Parameters (Time, Position, Satellite Data)
CONTENTS
Present time
Current position
Hold position [*1]
Ephemeris
Almanac
PARAMETER
HOT
WARM
COLD
FACTORY
Date & Time
Millennium
Latitude
Longitude
Altitude
Latitude
Longitude
Altitude
Ephemeris data
Almanac data
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
POWER
OFF/ON
YES
YES
YES
YES
YES
YES [*2]
YES [*2]
YES [*2]
YES [*3]
YES
[*1] Back up only when the survey position has been calculated or the position mode is set to TO mode by
SURVEY command.
[*2] CSS mode or TO mode only.
[*3] Expiration date is maximum 4 hours in case of GPS.
Table 8.2 Backup of Communication Setting
COMMAND
NAME
UART1
NMEAOUT
PARAMETER
Baud rate of
UART1
NMEA output
interval
HOT
WARM
COLD
FACTORY
POWER
OFF/ON
YES
YES
YES
YES
NO
YES
YES
YES
YES
NO
67
GT-88
Protocol Specifications
SE18-600-003-00
Table 8.3 Backup of Command Setting
COMMAND
NAME
GNSS
PPS
FREQ
SURVEY
DEFLS
TIMEZONE
TIMEALIGN
FIXMASK
OCP
NLOSMASK
ECLKCNT
ECLK
CROUT
ANTSEL
PARAMETER
HOT
WARM
COLD
FACTORY
GNSS setting
PPS setting
FREQ setting
position mode
Sigma threshold
Time threshold
Calculation process of
survey position
Default leap second
LZT setting
Time alignment
FIXMASK setting
OCP setting
NLOS satellite
elimination setting
ECLKCNT output
setting
ECLK mode setting
CR sentence output
setting
Antenna input setting
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
POWER
OFF/ON
YES
YES
YES
YES
YES
YES
YES [*1]
YES [*1]
YES [*1]
NO
YES [*1]
YES
YES
YES
YES
NO
YES
YES
YES
YES
NO
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
NO
YES
YES
YES
NO
YES
NO
NO
NO
NO
NO
YES
YES
YES
NO
YES
YES
YES
YES
NO
YES
YES
YES
YES
YES
NO
[*1] CSS mode or TO mode only.
68
GT-88
Protocol Specifications
SE18-600-003-00
9 Insertion of Leap Second
This product outputs the time information as shown below when a leap second is adjusted.
[Leap second (+1) insertion]
When inserting a leap second (+1), 23:59:60 is inserted at the update timing.
The table below shows an example.
GPS time
1009411213
1009411214
1009411215
1009411216
1009411217
1009411218
UTC date
December 31, 2011
December 31, 2011
December 31, 2011
January 1, 2012
January 1, 2012
January 1, 2012
UTC time
23:59:58
23:59:59
23:59:60
00:00:00
00:00:01
00:00:02
[Leap second (-1) insertion]
When inserting a leap second (-1), 23:59:59 is removed at the update timing.
The table below shows an example.
GPS time
1056672013
1056672014
1056672015
1056672016
1056672017
UTC date
June 30, 2013
June 30, 2013
July 1, 2013
July 1, 2013
July 1, 2013
69
UTC time
23:59:57
23:59:58
00:00:00
00:00:01
00:00:02
GT-88
Protocol Specifications
SE18-600-003-00
10 Instructions and Directions for Use
In case of using GLONASS satellite with this product, please use a multi-GNSS antenna. When setting to use
GLONASS with GPS antenna, GLONASS signals may be received in rare case. However, this product does
not guarantee the operation in this state.
GLONASS does not prescribe the behavior of navigation message when leap second is inserted. Therefore,
tracking and positioning of GLONASS may be temporarily interrupted depending on the behavior of the
navigation message broadcast by GLONASS at the timing when leap second is inserted. In addition, it may be
necessary to restart positioning resumption.
In case of selecting GLONASS and the other satellites (GPS/Galileo/QZSS) together, this product uses
GLONASS in position fix after the time is fixed with either GPS/Galileo/QZSS. Therefore, when it cannot
receive the required number of GPS/Galileo/QZSS for position fix, it may not do position fix with GLONASS
satellites. However, in case of GLONASS standalone positioning, GLONASS positioning is immediately
performed.
Galileo and GLONASS satellites output parameters for converting the time system of each satellite to GPS
time. According to ICD, it is defined as follows.
GGTO: Difference between Galileo time and GPS time
tauGPS: Difference between GLONASS time and GPS time
GGTO is broadcasted from the Galileo satellite in a cycle of 60 seconds, and tauGPS is broadcasted from the
GLONASS satellite in a cycle of 30 seconds.
When setting to use multiple satellites including Galileo (e.g. GPS+Galileo) with GNSS command, Galileo will
not be used for positioning until GGTO acquisition. However, when using Galileo alone, positioning will start
without waiting for GGTO acquisition. In this case, 1PPS is output at Galileo time until GGTO acquisition even
if 1PPS is set to GPS synchronization.
As of 2018, QZSS has fewer satellites being operated compared to GPS and GLONASS. Therefore,
depending on the time zone it may not be received because it is located at a low elevation angle. We
recommend that you use QZSS in conjunction with other satellites in order to ensure consistent time output
and positioning continuously.
QZSS satellites do not broadcast parameters for converting to GPS time like GGTO of Galileo satellite or
tauGPS of GLONASS satellite. Therefore, 1PPS is output in synchronization with the QZSS time even if 1PPS
is set to GPS synchronization.
This product implements a mechanism to check the consistency of the message content of the signal received
from the antenna. Therefore if the product is connected to the simulator after positioning with the actual
satellite in the continuous energized state without turning the power OFF/ON or restarting, or vice versa,
positioning may not be performed. The case that the simulator scenario is changed in the middle is the same.
In this case, positioning can be performed by executing power OFF/ON or by sending a RESTART command.
Details of the specifications other than the protocol of this product are also described in the hardware
specifications.
70
GT-88
Protocol Specifications
SE18-600-003-00
11 FAQ
Q. The receiver cannot receive satellite signals. What kind of causes can you think of?
A.
Please check whether this product and the antenna are properly connected. Especially when the signal
level is low as a whole, there is a possibility that proper gain may not be maintained even if this product
and the antenna are physically connected by cables.
Q. Even though the antenna setting is appropriate, positioning is not possible. What kind of causes
can you think of?
A.
Among the commands being backed up, there may be a factor impeding positioning. Or, positioning may
not be possible since almanac data being backed up is abnormal. In this case, execute FACTORY COLD
with the RESTART command and erase all backups with the FLASHBACKUP command.
Q. Is there a command to output the almanac acquisition time?
A.
eSIP protocol does not have such command.
Q. Is there an expiration date for the almanac?
A.
With this product, the almanac has no expiration date.
Q. In case of any abnormality in this product, how is it notified?
A.
When this product finds an unexpected exception processing, it will automatically restart after outputting
the following message. “*” in the message indicates the register value, and “xx” indicates the type of
exception.
71
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